Rejecting International Email

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Re: Rejecting International Email

Zbigniew Szalbot-9
Hello,

/dev/rob0 pisze:

> Please check your attributions and reread the thread. In no place did I
> advocate this, and in fact in my portion of the quoted text I doubted
> the usefulness of this approach. It's "net-friendly" only in that it
> makes a single DNS query to the zone.

Apologies - I sent it to the list and I thought it was clear I was
referring to original poster. I absolutely agree with you on this! I am
sorry for this confusion.

--
Zbigniew Szalbot
www.lc-words.com

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Re: Rejecting International Email

mouss-2
In reply to this post by jason hirsh
Jason Hirsh wrote:

>
> On Apr 29, 2008, at 12:08 PM, Carlos Williams wrote:
>
>> I am currently running Postfix postfix-2.2.10-1.1.el4 and I am finding
>> a few spam emails slip through the cracks that are from .ca, nz, jp,
>> nl, and other common countries known for spam. Is there a way I can
>> have Postfix reject all email except for .mil, .edu, .us, .com, .net,
>> .org, and other legit domain extensions?
>>
>> I tried searching Google and the Postfix site but was not sure if my
>> verbiage was correct. I don't know where this would go. I would assume
>> this would be a header_check parameter but how that appears I just
>> don't know...
>>
>> Anyone care to assist me in this matter?
>>
>> I don't know if it matters so here are some logs of them slipping
>> through:
>>
>> [root@mail ~]# cat /var/log/maillog | grep "<[hidden email]>"
>> Apr 29 11:35:26 mail postfix/qmgr[29577]: C305D15C06C:
>> from=<[hidden email]>, size=913, nrcpt=1 (queue active)
>> Apr 29 11:35:26 mail postfix/qmgr[29577]: 47F0815C06E:
>> from=<[hidden email]>, size=1368, nrcpt=1 (queue active)
>> Apr 29 11:35:26 mail amavis[1320]: (01320-11) Passed CLEAN,
>> [72.248.68.127] [72.248.68.127] <[hidden email]> ->
>> <[hidden email]>, Message-ID:
>> <000801c8aa0e$0310717c$c30cc995@oldrwvj>, mail_id: phcAFLJ4UAyB, Hits:
>> -, size: 913, queued_as: 47F0815C06E, 125 ms
>>
>> There are more I am sure...
>>
>> Thanks for any info!
>
>
> This is a little coarse but it sure gets rid of the offending countries
> I am sure there are subtler methods...but I don't get a lot of mail
> from foreign countries so
> I added this to my main.cf
>
>
> smtpd_sender_restrictions = reject_rhsbl_sender dsn.rfc-ignorant.org
>     reject_rbl_client kr.countries.nerd.dk
>     reject_rbl_client cn.countries.nerd.dk
>     reject_rbl_client zen.spamhaus.org
>     reject_rbl_client bl.spamcop.net
>     reject_rbl_client kp.countries.nerd.dk
>     reject_rbl_client ng.countries.nerd.dk
>     reject_rbl_client tw.countries.nerd.dk
>     reject_rbl_client th.countries.nerd.dk
>     reject_rbl_client pl.countries.nerd.dk
>     reject_rbl_client ru.countries.nerd.dk
>     reject_rbl_client it.countries.nerd.dk
>     reject_rbl_client cz.countries.nerd.dk
>      reject_rbl_client ae.countries.nerd.dk
>      reject_rbl_client br.countries.nerd.dk
>      reject_rbl_client PE.countries.nerd.dk
>      reject_rbl_client MX.countries.nerd.dk
>     reject_rbl_client tr.countries.nerd.dk

oh, really?

$ host 204.127.131.115
115.131.127.204.in-addr.arpa domain name pointer mtiwmhc11.worldnet.att.net.
$ host 204.127.131.116
116.131.127.204.in-addr.arpa domain name pointer mtiwmhc12.worldnet.att.net.
$ host 204.127.131.117
117.131.127.204.in-addr.arpa domain name pointer mtiwmhc13.worldnet.att.net.
$ host 204.127.131.118
118.131.127.204.in-addr.arpa domain name pointer mtiwmxc18.worldnet.att.net.
$ host 204.127.131.119
Host 119.131.127.204.in-addr.arpa not found: 3(NXDOMAIN)
...
$ host 204.127.131.121
121.131.127.204.in-addr.arpa domain name pointer mtiwmxc11.worldnet.att.net.
$ host 204.127.131.122
122.131.127.204.in-addr.arpa domain name pointer mtiwmxc12.worldnet.att.net.
$ host 204.127.131.123
123.131.127.204.in-addr.arpa domain name pointer mtiwmxc13.worldnet.att.net.

sounds like a candidate for sorbs duhl. and in any case, is good for:

    check_client_access pcre:/etc/postfix/maps/pcre/grdns

/^mti.*\d{2,}\.worldnet\.att\.net$/    554 5.7.1 generic hostname.
please use your ISP relay or fix your rDNS.






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RE: Rejecting International Email

MacShane, Tracy
In reply to this post by /dev/rob0
 > -----Original Message-----

> From: [hidden email]
> [mailto:[hidden email]] On Behalf Of /dev/rob0
> Sent: Wednesday, 30 April 2008 4:08 AM
> To: [hidden email]
> Subject: Re: Rejecting International Email
>
> On Tue April 29 2008 12:12:46 Colin Brace wrote:
> > On Tue, 29 Apr 2008 12:08:13 -0400, "Carlos Williams"
> > <[hidden email]> wrote:
> > > I am currently running Postfix postfix-2.2.10-1.1.el4 and I am
> > > finding a few spam emails slip through the cracks that are from
.ca,
> > > nz, jp, nl, and other common countries known for spam. Is there a
> > > way I can have Postfix reject all email except for .mil, .edu,
.us,

> > > .com, .net, .org, and other legit domain extensions?
>
> Interesting choice of words, to imply that CCTLD's are
> somehow not legitimate.
>
> > There are more intelligent and effective ways of dealing with spam
> > then blocking entire countries. See this essay:
>
> That's true, and furthermore it was not clear whether the OP
> knew what he meant in saying these spams were "from" these
> nasty, evil spamming countries. I suspect he was seeing
> sender addresses, or worse, the "From:" header, which as has
> already been pointed out in this thread, is meaningless.
>

I totally agree with this post. Anyone who cites .ca, .nl, and .nz
(please!) as top-spamming CCTLDs without apparently being aware of .cn,
.ru and .kr *hosts* (not sender domains) is in a world of their own.

There are much better ways of blocking spam, and using a reputable RBL
like zen.spamhaus.org should be a primary line of defense.
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Re: Rejecting International Email

Terry Carmen
In reply to this post by Arturo 'Buanzo' Busleiman
You guys are all having a great time dumping on this guy.

He might not have expressed what he wants to do in terms that suit you
all, but the idea is sound.

Some businesses are strictly local and have no need to accept mail from
outside their geographic region. Regardless of whether or not most spam
comes from the US (I don't know and it's not relevant), it's perfectly
reasonable to only accept mail from locations you do business with.

For example, one of my clients, has business locations and customers in
the eastern US. They couldn't care less if someone from outside this
area sends mail, since it's physically impossible to service them (the
delivery trucks have a hard time crossing the ocean).

By only accepting connections from systems inside the geographic area
they service, literally millions of spams/month can simply be ignored,
with zero lost business.

It's hard to argue with success.

Terry

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Re: Rejecting International Email

vg_us
--------------------------------------------------
From: "Terry Carmen" <[hidden email]>
Sent: Tuesday, April 29, 2008 9:46 PM
Cc: "Postfix users" <[hidden email]>
Subject: Re: Rejecting International Email

> You guys are all having a great time dumping on this guy.
>
> He might not have expressed what he wants to do in terms that suit you
> all, but the idea is sound.
>
> Some businesses are strictly local and have no need to accept mail from
> outside their geographic region. Regardless of whether or not most spam
> comes from the US (I don't know and it's not relevant), it's perfectly
> reasonable to only accept mail from locations you do business with.
>
> For example, one of my clients, has business locations and customers in
> the eastern US. They couldn't care less if someone from outside this area
> sends mail, since it's physically impossible to service them (the delivery
> trucks have a hard time crossing the ocean).
>
> By only accepting connections from systems inside the geographic area they
> service, literally millions of spams/month can simply be ignored, with
> zero lost business.
>
> It's hard to argue with success.
>
> Terry
>
>

really? and what if his client with say hotmail or google address sends him
email from right region, but his provider round-trips it through california
because of some screwed up load balancing setup? business lost?
and what to do about addresses not matching regions? like all of the M$?

 

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Re: Rejecting International Email

jason hirsh

On Apr 29, 2008, at 9:58 PM, <[hidden email]> wrote:

> --------------------------------------------------
> From: "Terry Carmen" <[hidden email]>
> Sent: Tuesday, April 29, 2008 9:46 PM
> Cc: "Postfix users" <[hidden email]>
> Subject: Re: Rejecting International Email
>
>> You guys are all having a great time dumping on this guy.
>>
>> He might not have expressed what he wants to do in terms that suit  
>> you all, but the idea is sound.
>>
>> Some businesses are strictly local and have no need to accept mail  
>> from outside their geographic region. Regardless of whether or not  
>> most spam comes from the US (I don't know and it's not relevant),  
>> it's perfectly reasonable to only accept mail from locations you do  
>> business with.
>>
>> For example, one of my clients, has business locations and  
>> customers in the eastern US. They couldn't care less if someone  
>> from outside this area sends mail, since it's physically impossible  
>> to service them (the delivery trucks have a hard time crossing the  
>> ocean).
>>
>> By only accepting connections from systems inside the geographic  
>> area they service, literally millions of spams/month can simply be  
>> ignored, with zero lost business.
>>
>> It's hard to argue with success.
>>
>> Terry
>>
>>
>
> really? and what if his client with say hotmail or google address  
> sends him email from right region, but his provider round-trips it  
> through california because of some screwed up load balancing setup?  
> business lost?
> and what to do about addresses not matching regions? like all of the  
> M$?
>
>
I thought we were talking about international.   if hotmail is  
bouncing through bulgaria.. then maybe users should find a new provider.

I got some good tips on how to be more "net friendly"   but I did find  
blocking some countries in which in my case I have no dealings  
(bulgaria, malaysia and the like)  cut my spam down from 100s a day to  
a couple which are now being handled by spamassassin...

I tend to agree with terry

jason
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Re: Rejecting International Email

Jorey Bump
In reply to this post by Terry Carmen
Terry Carmen wrote, at 04/29/2008 09:46 PM:

> You guys are all having a great time dumping on this guy.
>
> He might not have expressed what he wants to do in terms that suit you
> all, but the idea is sound.
>
> Some businesses are strictly local and have no need to accept mail from
> outside their geographic region. Regardless of whether or not most spam
> comes from the US (I don't know and it's not relevant), it's perfectly
> reasonable to only accept mail from locations you do business with.
>
> For example, one of my clients, has business locations and customers in
> the eastern US. They couldn't care less if someone from outside this
> area sends mail, since it's physically impossible to service them (the
> delivery trucks have a hard time crossing the ocean).
>
> By only accepting connections from systems inside the geographic area
> they service, literally millions of spams/month can simply be ignored,
> with zero lost business.

Why do you assume such a close relationship between geography and the
Internet? In fact, I stopped blocking based on country when someone who
lived a mile away from me couldn't email my client who lived a block
away. Why not? Because unknown to him, his .com domain's web host and
email provider was based in Singapore. After his technical support
contact demonstrated that they were running a highly professional
service, I felt rather bigoted, and reevaluated my position. In any
case, business was being lost, due to my overly simplistic view of the
Internet.

> It's hard to argue with success.

One of my sites must accept email from every country in the world, so I
must be extremely careful about what I reject, and therefore run fewer
filters and scoring systems than on my other sites. Nonetheless, I've
reduced spam to a trickle. You really don't need to focus on country of
origin to significantly reduce spam. Noone's dumping on the OP, they are
simply sharing experience, and the consensus seems to be that blocking
based on country doesn't deliver much bang for the buck. Naturally, this
doesn't apply to those eeeeeevil Canadians!


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Re: Rejecting International Email

Terry Carmen
In reply to this post by vg_us

>> By only accepting connections from systems inside the geographic area
>> they service, literally millions of spams/month can simply be
>> ignored, with zero lost business.
>>
>>
>
> really? and what if his client with say hotmail or google address
> sends him email from right region, but his provider round-trips it
> through california because of some screwed up load balancing setup?
> business lost?
> and what to do about addresses not matching regions? like all of the M$?
Then you whitelist a few CIDRs. No big deal.

Terry

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Re: Rejecting International Email

Terry Carmen
In reply to this post by Jorey Bump
Jorey Bump wrote:
> Why do you assume such a close relationship between geography and the
> Internet?

Because the IP blocks are allocated by region, then by country.

Some are incorrectly listed, but these are aberrations that can be
easily corrected. Oracle, for example, has mail servers with IPs that
belong to RIPE, which are physically located in the US.

> In fact, I stopped blocking based on country when someone who lived a
> mile away from me couldn't email my client who lived a block away. Why
> not? Because unknown to him, his .com domain's web host and email
> provider was based in Singapore.
So you update your CIDR list and move on.
> After his technical support contact demonstrated that they were
> running a highly professional service, I felt rather bigoted, and
> reevaluated my position. In any case, business was being lost, due to
> my overly simplistic view of the Internet.
Only you can decide if any lost business is worth the reduction in spam.

However many businesses couldn't care less about foreign email, and
blocking is a good business decision. If, for example, your business
involves driving trucks to  customer sites, you probably couldn't care
less about international email, since it's physically impossible for
anyone outside your geographic area to be one of your customers.

The OP made a business decision, and wanted technical advice, and all he
got was the party line about being "open".

FWIW, I sent him an appropriate CIDR list and main.cfg entry.

Terry




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Re: Rejecting International Email

M. Fioretti-2
In reply to this post by Terry Carmen
On Tue, Apr 29, 2008 21:46:27 PM -0400, Terry Carmen wrote:

> Some businesses are strictly local and have no need to accept mail
> from outside their geographic region... it's perfectly reasonable to
> only accept mail from locations you do business with.
> For example, one of my clients, has business locations and customers
> in the eastern US... By only accepting connections from systems
> inside the geographic area they service, literally millions of
> spams/month can simply be ignored, with zero lost business.

as a freelance writer interested in F/OSS original stories, I
*continuously* surf the net searching for small businesses, big
businesses and NGOs worldwide. Whenever I end up writing an article,
it's good, free advertising for that organization, regardless of how
restricted their *current* business area is. Of course, if I cannot
reach them, no article, no publicity, no way others can know, for
example, that those people could use some suggestions on how to set up
some server.

This is an extreme, niche case? Probably. Let's see some other ones
them:

- my MX is in a country different from where I live, because it is
  cheaper and more convenient/reliable for many other reasons which
  are irrelevant right now. Millions of businesses worldwide still do
  the same because it does make sense in many cases. Should the shop
  or insurance agency ten blocks away from my computer reject an info
  request because it "came" from abroad?

- think people who are considering _relocating_ to your area and want
  to check if they could use your services once they move

- you mentioned "business locations and customers": what about
  suppliers whose warehouses or central offices are far from one's
  business area?

- goodbye to any technical (in the broadest sense) support through
  mailing list or web forums with email notification, unless, of
  course, they accept to relocate their servers in your area code when
  you subscribe

- let's not even mention fiscal, legal and similar communications with
  central Public Administrations, or credit card companies, if you
  restrict the area to anything less than your whole country.

> It's hard to argue with success.

frankly, it's hard for me to see how such an approach can be
guaranteed as "success", or make any sense in the real world outside
very few, very special cases.

                Marco
--
Your own civil rights and the quality of your life heavily depend on how
software is used *around* you:            http://digifreedom.net/node/84
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Re: Rejecting International Email

/dev/rob0
In reply to this post by Terry Carmen
On Tue April 29 2008 20:46:27 Terry Carmen wrote:
> You guys are all having a great time dumping on this guy.

And you come along to try to spoil the fun? Fragile feelings (on your
own behalf, or vicariously on behalf of others) will not help anyone
who is trying to understand technical issues.

> He might not have expressed what he wants to do in terms that suit
> you all, but the idea is sound.

No, not really. Your followup posts talked about CIDR and IP address
assignments, which has nothing to do with what the OP wants to block:
sender addresses from "non-legitimate" ccTLD's. Spam havens like .ca,
.nl, .nz and others.

I am a perfect example of problems with that. I'm not in UK. I know a
chap who moved from UK to tn.us, and of course he kept his .uk domain
name after the move. Suppose I tried to use this email address to order
a birthday cake for my kid? Should the bakery ignore senders who are
not "from" a short, arbitrary TLD list?

> Some businesses are strictly local and have no need to accept mail
> from outside their geographic region. Regardless of whether or not

No *typical* need, sure. Possibly not ever. It depends in part how
much/what kind of risk you want to take.

#include Marco's post /* thanks Marco, well done*/

> most spam comes from the US (I don't know and it's not relevant),
> it's perfectly reasonable to only accept mail from locations you do
> business with.

Except as noted by Marco, and again, as noting your apparent
misunderstanding of the supposedly sound idea.

> For example, one of my clients, has business locations and customers
> in the eastern US. They couldn't care less if someone from outside
> this area sends mail, since it's physically impossible to service
> them (the delivery trucks have a hard time crossing the ocean).

But those trucks are built using parts and components from everywhere.
You cannot be so certain that your client will never need mail from
outside the local area. You can gamble, and sure, most of the time
you'll win that one.

> It's hard to argue with success.

It's easy to argue with incomplete understanding and overrestricted
thinking.

Sure, block all sender domains outside of gTLD's and .us. (But don't
try using a cidr_table(5) for check_sender_access.) Or just block any
random 20 SMTP connections. Most of those are spam. But was it a safe
and reasonable criterion for blocking?

The funny thing: the OP has indeed started on some sound anti-spam
approaches, as his posts to this list have shown. You're not helping
him by encouraging a bad idea.
--
    Offlist mail to this address is discarded unless
    "/dev/rob0" or "not-spam" is in Subject: header
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Re: Rejecting International Email

Zbigniew Szalbot-9
In reply to this post by M. Fioretti-2
Hi,

M. Fioretti pisze:

> as a freelance writer interested in F/OSS original stories, I
> *continuously* surf the net searching for small businesses, big
> businesses and NGOs worldwide. Whenever I end up writing an article,
> it's good, free advertising for that organization, regardless of how
> restricted their *current* business area is. Of course, if I cannot
> reach them, no article, no publicity, no way others can know, for
> example, that those people could use some suggestions on how to set up
> some server.
>
> This is an extreme, niche case? Probably. Let's see some other ones
> them:
One of them could be that for some reason a worker in a local business
wants to broaden his knowledge of whatever and subscribes to a mailing
list hosted in "judging-by-CIDRs" third world country?

Regards,

--
Zbigniew Szalbot
www.lc-words.com

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Re: Rejecting International Email

Jason Pruim
Hi Everyone,

I'm not really responding to anyone thread in particular I just wanted  
to share my experience... I have a friend who is a missionary in quito  
Ecuador. He sends out e-mails to keep his supporters and friends up to  
date on what he is doing, how's it going, etc. etc.. A while back he  
started to run into all kinds of trouble with his e-mail provider  
being blocked by USA based ISP's because of the fact that it was based  
in ecuador.

No amount of talking to people could get it fixed, and he ended up  
moving his entire distribution list over to a mailman mailing list  
hosted on my us based server and signing up for a gmail account just  
so that he could correspond with his friends back here in the states.

Now... what if one of your employees has a friend that is a  
missionary? Is it fare to make them signup for a different e-mail  
account assuming the one they have already is working for everyone but  
a few people?

I guess what I'm getting at is I feel there are better ways to stop  
spam... For me, until recently, greylisting took care of almost all my  
spam.. Now I need to look into other things like content scanners, and  
a few things like that.

Anyway, just my 2¢ :)




--

Jason Pruim
Raoset Inc.
Technology Manager
MQC Specialist
3251 132nd ave
Holland, MI, 49424-9337
www.raoset.com
[hidden email]



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Re: Rejecting International Email

Paweł Leśniak
Jason Pruim pisze:

> Now... what if one of your employees has a friend that is a
> missionary? Is it fare to make them signup for a different e-mail
> account assuming the one they have already is working for everyone but
> a few people?
>
> I guess what I'm getting at is I feel there are better ways to stop
> spam... For me, until recently, greylisting took care of almost all my
> spam.. Now I need to look into other things like content scanners, and
> a few things like that.
>
> Anyway, just my 2¢ :)
OK. So I'll also give my 2¢ :)
If I were to do such a thing, I'd block not hosts according to
DNS/Whois/etc. but rather language used in email. If someone is *sure*
that his users don't actually get *ANY* emails written in polish or
lithuanian(?) or swahili - why not just block it. It's not IP/DNS
dependent solution, so one can be sure that when he's on vacations he'll
still be able to send/receive emails. SpamAssassin can do that, but it's
not at SMTP session so it's not a really good solution. Maybe there are
better ways to do this.

P.

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Re: Rejecting International Email

Terry Carmen
In reply to this post by M. Fioretti-2
M. Fioretti wrote:

> On Tue, Apr 29, 2008 21:46:27 PM -0400, Terry Carmen wrote:
>
>  
>> Some businesses are strictly local and have no need to accept mail
>> from outside their geographic region... it's perfectly reasonable to
>> only accept mail from locations you do business with.
>> For example, one of my clients, has business locations and customers
>> in the eastern US... By only accepting connections from systems
>> inside the geographic area they service, literally millions of
>> spams/month can simply be ignored, with zero lost business.
>>    
>
> as a freelance writer interested in F/OSS original stories, I
> *continuously* surf the net searching for small businesses, big
> businesses and NGOs worldwide. Whenever I end up writing an article,
> it's good, free advertising for that organization, regardless of how
> restricted their *current* business area is. Of course, if I cannot
> reach them, no article, no publicity, no way others can know, for
> example, that those people could use some suggestions on how to set up
> some server.
>  
If your message is rejected, the 5xx reject contains a toll free number
to call to be whitelisted.

...

Many other examples deleted.
...

You're missing the point, that this is a business decision, not a
technical decision.

Until SMTP is replaced or enhanced so that each message is guaranteed to
come from a verifiable (and blockable) individual person, companies will
continue to use more and more draconian measures to keep their email usable.

Sure, it would be nice to accept email from everywhere, but email costs
money when it gets out of hand. By blocking mail from unwanted
geographic locations, they're able to handle all their email on three
servers running at a low utilization level with a couple of admins.
Since more than 95% of their inbound is spam, I'll let you do the math
as to what the hardware and payroll costs would be if it was necessary
to accept and process each message from anywhere.

Do you know what's worse for business than a friendly reject message
that contains a toll-free number? Accepting a customer message, then
mistakenly deleting it as spam.

Terry

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Re: Rejecting International Email

Erwan David
In reply to this post by Paweł Leśniak
On Wed, Apr 30, 2008 at 02:43:14PM CEST, Paweł Leśniak <[hidden email]> said:
> OK. So I'll also give my 2¢ :)
> If I were to do such a thing, I'd block not hosts according to  
> DNS/Whois/etc. but rather language used in email. If someone is *sure*  
> that his users don't actually get *ANY* emails written in polish or  
> lithuanian(?) or swahili - why not just block it. It's not IP/DNS  
> dependent solution, so one can be sure that when he's on vacations he'll  
> still be able to send/receive emails. SpamAssassin can do that, but it's  
> not at SMTP session so it's not a really good solution. Maybe there are  
> better ways to do this.

It may work, but be aware that language is difficult to detect, and
you can receive mails written in english but using Big5 charset (or
any charset containing ascii).

Even my mail will be sent in UTF-8 (because I made a citation of
your name, and I did not configure to use ISO-8859-2)

--
Erwan
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Re: Rejecting International Email

Terry Carmen
In reply to this post by Jason Pruim

> I'm not really responding to anyone thread in particular I just wanted
> to share my experience... I have a friend who is a missionary in quito
> Ecuador. He sends out e-mails to keep his supporters and friends up to
> date on what he is doing, how's it going, etc. etc.. A while back he
> started to run into all kinds of trouble with his e-mail provider
> being blocked by USA based ISP's because of the fact that it was based
> in ecuador.
>
> No amount of talking to people could get it fixed, and he ended up
> moving his entire distribution list over to a mailman mailing list
> hosted on my us based server and signing up for a gmail account just
> so that he could correspond with his friends back here in the states.
>
> Now... what if one of your employees has a friend that is a
> missionary? Is it fare to make them signup for a different e-mail
> account assuming the one they have already is working for everyone but
> a few people?
There is a company email policy that prohibits personal email on company
email addresses. If they want to subscribe to a mailing list from
Ecuador, they're welcome to use the external email provider of their choice.

> I guess what I'm getting at is I feel there are better ways to stop
> spam... For me, until recently, greylisting took care of almost all my
> spam.. Now I need to look into other things like content scanners, and
> a few things like that.
We tried greylisting. It's a little helpful, but the delay was really
annoying the users. And for large companies that bounce outbound mail
around to multiple servers after a 4xx reject, some messages would never
get through because the greylist time would expire before that
sender/recipient/sending ip came back around.


Terry

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Re: Rejecting International Email

Erwan David
On Wed, Apr 30, 2008 at 02:58:16PM CEST, Terry Carmen <[hidden email]> said:
>
> We tried greylisting. It's a little helpful, but the delay was really  
> annoying the users. And for large companies that bounce outbound mail  
> around to multiple servers after a 4xx reject, some messages would never  
> get through because the greylist time would expire before that  
> sender/recipient/sending ip came back around.

The fact is that filtering decisions are hard to take, because of the
false positive, and finaly depends on what you are ready to loose in
the fitering. Each decision is unique, but must be taken while
thunking to  all implications

--
Erwan
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Re: Rejecting International Email

Paweł Leśniak
In reply to this post by Erwan David
Erwan David pisze:
> It may work, but be aware that language is difficult to detect, and
> you can receive mails written in english but using Big5 charset (or
> any charset containing ascii).
>
> Even my mail will be sent in UTF-8 (because I made a citation of
> your name, and I did not configure to use ISO-8859-2)
>  
OK. With UTF-8 it's hard to detect in what language is the message
written (but SpamAssassin still can do that by checking which portion of
UTF charset You're using). But You don't use ISO-8859-2 or KOI-8R to
write a message ever. Unless You write in these charsets and that's when
You are from country which needs this encodings. I know it's not a
*real* solution. But still in my opinion it's way better than rejecting
mail by IP/Domain.

P.


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Re: Rejecting International Email

M. Fioretti-2
In reply to this post by Terry Carmen

On Wed, April 30, 2008 2:49 pm, Terry Carmen wrote:
> You're missing the point, that this is a business decision, not a
> technical decision.

The point is that this so-called "business decision":

>>> only accepting connections from systems inside the geographic area
>>> they service

is:

1) first of all, hugely different, dynamic, totally unpredictable and out
   of your clients control, from "only accepting connections from REAL
   customers
   or potential customers who LIVE AND WORK "inside the geographic area
   they service"", which is what you are suggesting to do

2) even IF 1) and what you suggest to do where the same thing, there still
   are cases where it doesn't make sense to act that way

Last but not least: the assumption that potential customers who get a
rejection message with a toll free number (which would mean spamming: why
_answer_ to messages which you are sure are spam?) would be:

savy enough to understand what to do and above all,

bothered to call to be whitelisted instead of just email another supplier
is as naive as the one that C-R systems are a good idea: the only people
who waste their time this way are likely to be those to whom you ALREADY
owe
money.

This said, if you haven't got the point yet, in spite of several detailed,
real world example by several people, I have really nothing to add. It's
your (actually, your clients...) problem only.

Marco
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