Postfix "IPv6-only" - experience/recommendation question

classic Classic list List threaded Threaded
27 messages Options
12
Reply | Threaded
Open this post in threaded view
|

Postfix "IPv6-only" - experience/recommendation question

michaelof@rocketmail.com
Hi all,


I've a generic question to all more experienced than me postfix users here: Is it nowadays (reasonable) possible to run postfix with IPv6 only? E.g  "mail.example.com" and "smtp.example.com" with only ipv6 AAAA records in the DNS, no A / ipv4 anymore?


Michael


----- EOM for impatient readers :-) -------


Hi patient readers :-)

reason for my question:

I'm running my own small postfix/dovecot etc. environment on a VPS. Running fine for years now, after some initial work to get my sent emails not delivered as junk.
spf record exists for my few domains, dkim is active and passes everytime, dmarc entry is active.
https://www.mail-tester.com gives me 10/10 :-)

All relevant for me email providers are accepting my emails without any issue, for long, except Microsoft hotmail/outlook. Registered for SNDS, and JMRP feed is activated.
IPv4 adress is "clean" and fine for outlook.com.

BUT nevertheless all emails from me to any outlook.* or hotmail.* recipients is delivered to their junk folder.

I strongly believe that this is because of the (hopefully) only "issue" left I know about: My PTR.

As I have a small VPS with only one IPV4 included in price, I've set the PTR to "example.com" and not to "mail.example.com", which is the fqdn for my outgoing postfix sent mail.
Of course I know that this is a "should not", but as there's a lot of stuff running e.g. on Apache on this machine, a nextcloud instance, a TYPO3 instance, roundcubemail, jitsi meet, ..., all on separate subdomains like "cloud.example.com", "webmail.example.com", "meet.example.com" etc., I simply don't like to have an "unclean" PTR, pointing not the main/base domain. "Only" because of antispam.

As said I have only one IPv4 for my VPS, but a /64 IPv6 subnet.
So more than enough IPv6 addreses to give each of my few domains amd not that many subdomains a unique IPv6, with a corresponding PTR.

I'm only not sure if there might be "IPv4-only" email providers out there, whose emails might not be routed to my "IPv6-only" postfix.

Sorry for this long email :-)



Regards,
Michael
Reply | Threaded
Open this post in threaded view
|

Re: Postfix "IPv6-only" - experience/recommendation question

Gerald Galster
Hi,

> I've a generic question to all more experienced than me postfix users here: Is it nowadays (reasonable) possible to run postfix with IPv6 only? E.g  "mail.example.com" and "smtp.example.com" with only ipv6 AAAA records in the DNS, no A / ipv4 anymore?

I would not yet advise to run a mail system ipv6 only.

> As I have a small VPS with only one IPV4 included in price, I've set the PTR to "example.com" and not to "mail.example.com", which is the fqdn for my outgoing postfix sent mail.
> Of course I know that this is a "should not", but as there's a lot of stuff running e.g. on Apache on this machine, a nextcloud instance, a TYPO3 instance, roundcubemail, jitsi meet, ..., all on separate subdomains like "cloud.example.com", "webmail.example.com", "meet.example.com" etc., I simply don't like to have an "unclean" PTR, pointing not the main/base domain. "Only" because of antispam.

The forward/reverse dns has to match but some providers also verify the helo name (postfix outgoing fqdn).

Why not run postfix with "example.com"? Other companies do not care if they deliver to example.com or mail.example.com.

> As said I have only one IPv4 for my VPS, but a /64 IPv6 subnet.
> So more than enough IPv6 addreses to give each of my few domains amd not that many subdomains a unique IPv6, with a corresponding PTR.

You can configure postfix to try ipv6 delivery first (which is the default for postfix 2.8+)

http://www.postfix.org/postconf.5.html#smtp_address_preference

> I'm only not sure if there might be "IPv4-only" email providers out there, whose emails might not be routed to my "IPv6-only" postfix.

That is possible.

Best regards
Gerald
Reply | Threaded
Open this post in threaded view
|

Re: Postfix "IPv6-only" - experience/recommendation question

allenc
In reply to this post by michaelof@rocketmail.com

On 08/05/2020 17:38, [hidden email] wrote:
> Hi all,
>
>
> I've a generic question to all more experienced than me postfix users here: Is it nowadays (reasonable) possible to run postfix with IPv6 only? E.g  "mail.example.com" and "smtp.example.com" with only ipv6 AAAA records in the DNS, no A / ipv4 anymore?
> I am running a domestic server, and 10 percent of inbound emails, and maybe 30
percent of outbound emails still use IPv4.

There was a worry some years ago that IPv6 was not adequately protected by DNS
blacklists, and was thus vulnerable to spam attacks. I have not found this
myself, but am not representative of the world-at-large.

But there seem to be a lot of MX hosts out there which do not accept incoming IPv6.

For my server, I have set up a primary MX which is IPv6 only, and a secondary,
which is dual protocol.  Perhaps you could do something similar with your situation.


Hope this helps

Allen C
Reply | Threaded
Open this post in threaded view
|

Re: Postfix "IPv6-only" - experience/recommendation question

Sean Greenslade
In reply to this post by michaelof@rocketmail.com
On Fri, May 08, 2020 at 06:38:32PM +0200, [hidden email] wrote:

> Hi all,
>
>
> I've a generic question to all more experienced than me postfix users here: Is it nowadays (reasonable) possible to run postfix with IPv6 only? E.g  "mail.example.com" and "smtp.example.com" with only ipv6 AAAA records in the DNS, no A / ipv4 anymore?
>
>
> Michael
>
>
> ----- EOM for impatient readers :-) -------
>
>
> Hi patient readers :-)
>
> reason for my question:
>
> I'm running my own small postfix/dovecot etc. environment on a VPS. Running fine for years now, after some initial work to get my sent emails not delivered as junk.
> spf record exists for my few domains, dkim is active and passes everytime, dmarc entry is active.
> https://www.mail-tester.com gives me 10/10 :-)
>
> All relevant for me email providers are accepting my emails without any issue, for long, except Microsoft hotmail/outlook. Registered for SNDS, and JMRP feed is activated.
> IPv4 adress is "clean" and fine for outlook.com.
>
> BUT nevertheless all emails from me to any outlook.* or hotmail.* recipients is delivered to their junk folder.
>
> I strongly believe that this is because of the (hopefully) only "issue" left I know about: My PTR.
>
> As I have a small VPS with only one IPV4 included in price, I've set the PTR to "example.com" and not to "mail.example.com", which is the fqdn for my outgoing postfix sent mail.
> Of course I know that this is a "should not", but as there's a lot of stuff running e.g. on Apache on this machine, a nextcloud instance, a TYPO3 instance, roundcubemail, jitsi meet, ..., all on separate subdomains like "cloud.example.com", "webmail.example.com", "meet.example.com" etc., I simply don't like to have an "unclean" PTR, pointing not the main/base domain. "Only" because of antispam.
>
> As said I have only one IPv4 for my VPS, but a /64 IPv6 subnet.
> So more than enough IPv6 addreses to give each of my few domains amd not that many subdomains a unique IPv6, with a corresponding PTR.
>
> I'm only not sure if there might be "IPv4-only" email providers out there, whose emails might not be routed to my "IPv6-only" postfix.

I have a suggestion that works well for my similar email setup (small
VPS providing a number of disparate services).

Give your VPS a hostname that's unrelated to any of the services. Mine,
for example, is "fenrir". Create an A / AAAA record for that hostname
underneath your domain. Make the PTR record point to that hostname FQDN.
Then you can point your MX records to that FQDN, and set up postfix to
identify itself as that same name.

Here's my DNS records:
fenrir.routify.me  - A   - <my IP address>
<my IP address>    - PTR - fenrir.routify.me
seangreenslade.com - MX  - fenrir.routify.me

And the greeting my Postfix gives:
220 fenrir.routify.me ESMTP Postfix

With this setup, I haven't had any issues with mail deliverability.

--Sean

Reply | Threaded
Open this post in threaded view
|

Re: Postfix "IPv6-only" - experience/recommendation question

Curtis Villamizar-2
In reply to this post by michaelof@rocketmail.com
In message <[hidden email]>
"[hidden email]" writes:
>
> Hi all,
>  
> I've a generic question to all more experienced than me postfix users
> here: Is it nowadays (reasonable) possible to run postfix with IPv6
> only? E.g "mail.example.com" and "smtp.example.com" with only ipv6
> AAAA records in the DNS, no A / ipv4 anymore?
>  
> Michael

Tried that but not for a few years.  Last I tried this in addition to
IPv6, you still need a routable (non-RFC1918) IPv4 address and valid
PTR for your MTA/MSA to reach some sites (like this mailing list last
I checked - but I rechecked and fixed now).  Alternately you need to
relay thru someone that has IPv4 and IPv6 but relay might be hard to
come by (never considered that).

IPv6 only is fine if you only send mail to the majors providers,
gmail, m$soft (live, msn, outlook, hotmail, etc), comcast, ... etc.
Less so if you send mail to enterprises (or individuals) that run
their own email and have IPv4 only.

What I have is a mostly IPv6 only network.  Dual mode are public
facing: DNS, web, MTA/MSA (most are VM).  I run multiple MDA (cyrus
imapd), one per domain, that are IPv6 only.  MTA does per domain relay
to MDA.  MDA does smarthost relay to MSA to handle bounce messages.
MTA does the prescreen and low overhead spam checks, MDA and a common
spamd host does more higher overhead checks with one honey pot domain
with its own web site to train filters (all mail to that domain is
spam).  Client hosts (cellphone, laptop) send to MSA (port 587).
Client to MSA and MTA to MDA uses DANE plus cyrus SASL and very strong
encryption, etc.  SASL is SCRAM256 only for MDA, SCRAM256 plus
DIGEST-MD5 for MSA due to limitations of some client MUA software but
this is within a TLS connection so DIGEST-MD5 is not so bad.

I do have two sites with 5 usable addresses each (/29 minus net,
bcast, router).  I have colo so you might have a bit more trouble
getting more IPv4 with VPS.  Easier a few years ago.  Why not point
your MX at example.com if you can only get one IPv4 address.

Hope this helps.

Curtis

> ----- EOM for impatient readers :-) -------
>  
> Hi patient readers :-)
>  
> reason for my question:
>  
> I'm running my own small postfix/dovecot etc. environment on a
> VPS. Running fine for years now, after some initial work to get my
> sent emails not delivered as junk.  spf record exists for my few
> domains, dkim is active and passes everytime, dmarc entry is active.
> https://www.mail-tester.com gives me 10/10 :-)
>  
> All relevant for me email providers are accepting my emails without
> any issue, for long, except Microsoft hotmail/outlook. Registered for
> SNDS, and JMRP feed is activated.  IPv4 adress is "clean" and fine for
> outlook.com.
>  
> BUT nevertheless all emails from me to any outlook.* or hotmail.*
> recipients is delivered to their junk folder.
>  
> I strongly believe that this is because of the (hopefully) only
> "issue" left I know about: My PTR.
>  
> As I have a small VPS with only one IPV4 included in price, I've set
> the PTR to "example.com" and not to "mail.example.com", which is the
> fqdn for my outgoing postfix sent mail.  Of course I know that this is
> a "should not", but as there's a lot of stuff running e.g. on Apache
> on this machine, a nextcloud instance, a TYPO3 instance,
> roundcubemail, jitsi meet, ..., all on separate subdomains like
> "cloud.example.com", "webmail.example.com", "meet.example.com" etc., I
> simply don't like to have an "unclean" PTR, pointing not the main/base
> domain. "Only" because of antispam.
>  
> As said I have only one IPv4 for my VPS, but a /64 IPv6 subnet.  So
> more than enough IPv6 addreses to give each of my few domains amd not
> that many subdomains a unique IPv6, with a corresponding PTR.
>  
> I'm only not sure if there might be "IPv4-only" email providers out
> there, whose emails might not be routed to my "IPv6-only" postfix.
>  
> Sorry for this long email :-)
>  
> Regards,
> Michael
Reply | Threaded
Open this post in threaded view
|

Re: Postfix "IPv6-only" - experience/recommendation question

Bill Cole-3
In reply to this post by michaelof@rocketmail.com
On 8 May 2020, at 12:38, [hidden email] wrote:

> Hi all,
>
>
> I've a generic question to all more experienced than me postfix users
> here: Is it nowadays (reasonable) possible to run postfix with IPv6
> only? E.g  "mail.example.com" and "smtp.example.com" with only ipv6
> AAAA records in the DNS, no A / ipv4 anymore?

No.

[...]

> I'm only not sure if there might be "IPv4-only" email providers out
> there, whose emails might not be routed to my "IPv6-only" postfix.

There are many.

Some do not yet have IPv6 service yet.

Some have IPv6 connectivity and address space but no motivation to make
their mail systems use IPv6. There are reasons to avoid sending over
IPv6 and very few if any significant reasons to want to send or receive
over IPv6. If one has a working IPv4-only mail system, adding IPv6 is
pure work for no discernible benefit.


--
Bill Cole
[hidden email] or [hidden email]
(AKA @grumpybozo and many *@billmail.scconsult.com addresses)
Not For Hire (currently)
Reply | Threaded
Open this post in threaded view
|

Re: Postfix "IPv6-only" - experience/recommendation question

Ralph Seichter-2
* Bill Cole:

> Some have IPv6 connectivity and address space but no motivation to
> make their mail systems use IPv6.

A case of what we call Public Servant Mikado (whoever moves first has
lost). ;-) Seriously, I think that if one can support IPv6, one should
do it. Good hosting services and ISPs already offer native IPv6, and
those that don't should be pressured by customer demand to get their act
together.

> If one has a working IPv4-only mail system, adding IPv6 is pure work
> for no discernible benefit.

Adding a static IPv6 address to a Linux host is a simple one-time effort
that takes a couple of minutes. Then, tweak some Postfix settings like
inet_interfaces, inet_protocols and maybe smtp_bind_address6. Create a
DNS AAAA record, update the SPF record.

Overall, I estimate that getting a Postfix-based MX IPv6-ready should
take about 15 minutes, and I think it is time well spent.

-Ralph
Reply | Threaded
Open this post in threaded view
|

Re: Postfix "IPv6-only" - experience/recommendation question

Viktor Dukhovni
In reply to this post by michaelof@rocketmail.com
On Fri, May 08, 2020 at 06:38:32PM +0200, [hidden email] wrote:

> I've a generic question to all more experienced than me postfix users
> here: Is it nowadays (reasonable) possible to run postfix with IPv6
> only? E.g  "mail.example.com" and "smtp.example.com" with only ipv6
> AAAA records in the DNS, no A / ipv4 anymore?

Yes, absolutely, provided the set of MTAs this server will communicate
with is known to be IPv6-capable.  Postfix works just fine with
IPv6-only in internal deployments.

If, however, you want to receive and send email to the Internet at
large, sadly you will not be able to send mail to, or receive mail
from, many potential destination domains without an IPv4 address.

--
    Viktor.
Reply | Threaded
Open this post in threaded view
|

Re: Postfix "IPv6-only" - experience/recommendation question

Bob Proulx
In reply to this post by Bill Cole-3
Bill Cole wrote:
> michaelof wrote:
> > I've a generic question to all more experienced than me postfix users
> > here: Is it nowadays (reasonable) possible to run postfix with IPv6
> > only? E.g  "mail.example.com" and "smtp.example.com" with only ipv6 AAAA
> > records in the DNS, no A / ipv4 anymore?
>
> No.

Agreed.  No.  You will not be able to exchange email with many sites.

> > I'm only not sure if there might be "IPv4-only" email providers out
> > there, whose emails might not be routed to my "IPv6-only" postfix.
>
> There are many.
>
> Some do not yet have IPv6 service yet.

I have a site using CenturyLink since that is the only option
available.  And CenturyLink there does not support IPv6!  Which I find
amazing but still true.  I am anxiously waiting for a city fiber
project which is every so slowly progressing so that a connection to
the new fiber ring might be made.  Until that time it has IPv4 only.

> Some have IPv6 connectivity and address space but no motivation to make
> their mail systems use IPv6. There are reasons to avoid sending over IPv6
> and very few if any significant reasons to want to send or receive over
> IPv6. If one has a working IPv4-only mail system, adding IPv6 is pure work
> for no discernible benefit.

How are working and available IPv6 DNSBLs progressing?  That's a
critical component which I would love to hear is no longer a missing
component.

Bob
Reply | Threaded
Open this post in threaded view
|

Re: Postfix "IPv6-only" - experience/recommendation question

Bill Cole-3
In reply to this post by Ralph Seichter-2
On 8 May 2020, at 15:06, Ralph Seichter wrote:

> * Bill Cole:
>
>> Some have IPv6 connectivity and address space but no motivation to
>> make their mail systems use IPv6.
>
> A case of what we call Public Servant Mikado (whoever moves first has
> lost). ;-)

Yes.

> Seriously, I think that if one can support IPv6, one should
> do it. Good hosting services and ISPs already offer native IPv6, and
> those that don't should be pressured by customer demand to get their
> act
> together.

Because I work in multiple unrelated environments, I see many sides of
this.

The boutique hosting/connectivity/services provider I work with (with 2
ASs, US & EU BGP presence, multiple IPv4 and IPv6 allocations) can
provide native IPv6 to customers. None ever has ever asked for it. The
main production mail hosting system has a /24 reserved for its use (and
mostly in use) and we've never had any technical reason to deploy IPv6
on it or customer demand. It's just not a thing with any pressure behind
it.

>
>> If one has a working IPv4-only mail system, adding IPv6 is pure work
>> for no discernible benefit.
>
> Adding a static IPv6 address to a Linux host is a simple one-time
> effort
> that takes a couple of minutes. Then, tweak some Postfix settings like
> inet_interfaces, inet_protocols and maybe smtp_bind_address6. Create a
> DNS AAAA record, update the SPF record.

Sure, for a one-IP Postfix system that's pretty easy.

However, if one has a clustered mail system that isn't Postfix with
scores of domains, each with their own IP on each of multiple nodes,
that's non-trivial work. For what? There is at least one large mail
system operator (Google) which explicitly has stricter criteria for
accepting mail from IPv6 sources, so    maybe you don't even want to
ever send on IPv6 anyway to avoid having to suit them today and a dozen
others with different criteria next week. Does anyone worth worrying
about only send or receive on IPv6?  Not that I'm aware of. Are there
tools for spam control of IPv6 incoming mail that match the IPv4 tools?
No.

> Overall, I estimate that getting a Postfix-based MX IPv6-ready should
> take about 15 minutes, and I think it is time well spent.

I'm not sure that it is for all mail operators, but even if I stipulate
the point: it's not what I was talking about.

The OP asked if IPv6-ONLY was practical. My reason for saying that it is
not (yet) was grounded in the reality that not all mail systems are
one-machine, one-IP, and/or Postfix. It's easy for anyone  with a
one-machine one-IP Postfix system and IPv6 connectivity and an assigned
/64 to be IPv6-READY with minimal effort. It isn't realistic to expect
that everyone you want to exchange mail with has those prerequisites
and/or has put out whatever effort their systems require to use IPv6 for
email.


--
Bill Cole
[hidden email] or [hidden email]
(AKA @grumpybozo and many *@billmail.scconsult.com addresses)
Not For Hire (currently)
Reply | Threaded
Open this post in threaded view
|

Re: Postfix "IPv6-only" - experience/recommendation question

Wietse Venema
In reply to this post by Bob Proulx
Bob Proulx:
> How are working and available IPv6 DNSBLs progressing?  That's a
> critical component which I would love to hear is no longer a missing
> component.

zen.spamhaus.org blocks some 15% of IPv6 spam for me. The other 85%
comes from large providers (outlook.com, gmail.com, etc) that aren't
blocked with DNSBLs.

        Wietse
Reply | Threaded
Open this post in threaded view
|

Re: Postfix "IPv6-only" - experience/recommendation question

Ralph Seichter-2
In reply to this post by Bill Cole-3
* Bill Cole:

> The boutique hosting/connectivity/services provider I work with [...]
> can provide native IPv6 to customers. None ever has ever asked for it.

That's quite a sweeping statement, and I don't believe it to be true.
For years I have asked every provider I have worked with if they offer
native IPv6, and if so in what net blocks etc. Unless you can provide
proof, in writing, I simply cannot believe that no customer has ever
asked the provider you mentioned for IPv6.

> There is at least one large mail system operator (Google) which
> explicitly has stricter criteria for accepting mail from IPv6 sources
> so maybe you don't even want to ever send on IPv6 anyway to avoid
> having to suit them today and a dozen others with different criteria
> next week.

Google has so far not rejected mail sent by the dual stack servers I
maintain, no matter if IPv4 or IPv6 was used. Both DKIM and SPF are
configured on my end, which seems to be a major concern for Google, but
beyond that I have neither noticed them being overly finicky nor
changing criteria often. YMMV.

> Does anyone worth worrying about only send or receive on IPv6? Not
> that I'm aware of.

The operative word being "only". That was indeed what the OP asked
about, and I forgot to mention that I too would not run an IPv6-only
mail server, same as you.

However, your question made me wonder: Is anyone worth worrying about,
as you put it, unable to send or receive via IPv6? While the answer is
possibly a yes in many cases (it is for me), I don't know how the OP
would be affected.

> Are there tools for spam control of IPv6 incoming mail that match the
> IPv4 tools?

Are there specific tools you have in mind which don't have IPv6 support
yet? Are the authors aware of that? Also, I look at it this way: Based
on my logs the amount of spam attempts, let alone deliveries, via IPv6
appears to be noticeably lower than via IPv4. I mean the ratio of spam
to connections, not only the absolute number. I wonder if that indicates
that spammers find it difficult to rent/purchase/employ IPv6-capable
infrastructure and spam tools?

-Ralph
Reply | Threaded
Open this post in threaded view
|

Re: Postfix "IPv6-only" - experience/recommendation question

Bill Cole-3
On 8 May 2020, at 17:26, Ralph Seichter wrote:

> * Bill Cole:
>
>> The boutique hosting/connectivity/services provider I work with [...]
>> can provide native IPv6 to customers. None ever has ever asked for it.
>
> That's quite a sweeping statement, and I don't believe it to be true.

Calling someone a liar is a very effective way to end a conversation.


--
Bill Cole
[hidden email] or [hidden email]
(AKA @grumpybozo and many *@billmail.scconsult.com addresses)
Not Currently Available For Hire
Reply | Threaded
Open this post in threaded view
|

Re: Postfix "IPv6-only" - experience/recommendation question

Ralph Seichter-2
* Bill Cole:

>> That's quite a sweeping statement, and I don't believe it to be true.
>
> Calling someone a liar is a very effective way to end a conversation.

Don't know if Trump supporter or trolling... I am a scientist, and thus
do not consider your claim to be true until you prove it. I have even
taken the time to tell you why.

Young people out there: The concept is called "facts", look it up.

-Ralph
Reply | Threaded
Open this post in threaded view
|

Re: Postfix "IPv6-only" - experience/recommendation question

allenc
In reply to this post by Wietse Venema


On 08/05/2020 21:58, Wietse Venema wrote:

> Bob Proulx:
>> How are working and available IPv6 DNSBLs progressing?  That's a
>> critical component which I would love to hear is no longer a missing
>> component.
>
> zen.spamhaus.org blocks some 15% of IPv6 spam for me. The other 85%
> comes from large providers (outlook.com, gmail.com, etc) that aren't
> blocked with DNSBLs.
>
> Wietse
>

That matches my experience...

Allen C
Reply | Threaded
Open this post in threaded view
|

Re: Postfix "IPv6-only" - experience/recommendation question

Jaroslaw Rafa
In reply to this post by Bill Cole-3
Dnia  8.05.2020 o godz. 14:33:16 Bill Cole pisze:
>
> Some have IPv6 connectivity and address space but no motivation to
> make their mail systems use IPv6. There are reasons to avoid sending
> over IPv6 and very few if any significant reasons to want to send or
> receive over IPv6. If one has a working IPv4-only mail system,
> adding IPv6 is pure work for no discernible benefit.

One of good reasons to NOT enable IPv6 may be the thing I heard when I was
dealing with my problem of being classified by Google as spam. Someone told
me (of course it's not confirmed, as there are virtually no confirmed
informations about how Google's anti-spam filter behaves) that Google is
more likely to classify email from small senders as spam if they are sent
via IPv6, and less likely if they are sent via IPv4.
--
Regards,
   Jaroslaw Rafa
   [hidden email]
--
"In a million years, when kids go to school, they're gonna know: once there
was a Hushpuppy, and she lived with her daddy in the Bathtub."
Reply | Threaded
Open this post in threaded view
|

Re: Postfix "IPv6-only" - experience/recommendation question

Jaroslaw Rafa
In reply to this post by Ralph Seichter-2
Dnia  8.05.2020 o godz. 23:26:06 Ralph Seichter pisze:
> Google has so far not rejected mail sent by the dual stack servers I
> maintain, no matter if IPv4 or IPv6 was used. Both DKIM and SPF are
> configured on my end, which seems to be a major concern for Google, but
> beyond that I have neither noticed them being overly finicky nor
> changing criteria often. YMMV.

They almost never reject, unless you send a really huge amount of messages
to them. They simply put your messages into recipient's Spam folder, so
he/she won't actually see it. It technically has been delivered, however
the recipient doesn't know it's there (as we shall remember that average
users almost never look into their Spam folders, unless explicitly told to -
and in that case they do it only once, when you tell them to). You, as the
sender, also don't know that it has been placed into Spam folder.
That's not only my experience, but many people here and there on the Net (on
this list as well) complain about that behaviour.
--
Regards,
   Jaroslaw Rafa
   [hidden email]
--
"In a million years, when kids go to school, they're gonna know: once there
was a Hushpuppy, and she lived with her daddy in the Bathtub."
Reply | Threaded
Open this post in threaded view
|

Re: Postfix "IPv6-only" - experience/recommendation question

michaelof@rocketmail.com
In reply to this post by Bob Proulx
THANKS to a all who answered!!!


A lot of shared experience, learned a lot, cool. It's always very interesting how threads are meandering, somehow, adding new aspects to unasked but also relevant questions. Crowd as it's best :-)
Summarized your valuable hints, I'll stay with my Postfix configured for both IPv4 and IPv6. No IPv6-only currently. Wait for the future.


Regards,
Michael


Reply | Threaded
Open this post in threaded view
|

Re: Postfix "IPv6-only" - experience/recommendation question

Gregory Heytings
In reply to this post by michaelof@rocketmail.com

[hidden email]:
>
> I've a generic question to all more experienced than me postfix users
> here: Is it nowadays (reasonable) possible to run postfix with IPv6
> only? E.g "mail.example.com" and "smtp.example.com" with only ipv6 AAAA
> records in the DNS, no A / ipv4 anymore?
>

In theory, yes: it is possible.  In practice, no: it won't work.  The vast
majority of mail servers do not (and will never) use IPv6.

I'd suggest you to read D. J. Bernstein's opinion on IPv6 (
http://cr.yp.to/djbdns/ipv6mess.html ).  He might be an unpleasant person,
but twenty years (!) later it seems reasonable to conclude that he was
mostly right, that it is regrettable his opinion was not taken into
account, and that IPv6 will never happen as it was supposed to happen.

Gregory
Reply | Threaded
Open this post in threaded view
|

Re: Postfix "IPv6-only" - experience/recommendation question

Curtis Villamizar-2
In reply to this post by michaelof@rocketmail.com
In message <[hidden email]>
"[hidden email]" writes:
 

> THANKS to a all who answered!!!
>  
> A lot of shared experience, learned a lot, cool. It's always very
> interesting how threads are meandering, somehow, adding new aspects to
> unasked but also relevant questions. Crowd as it's best :-) Summarized
> your valuable hints, I'll stay with my Postfix configured for both
> IPv4 and IPv6. No IPv6-only currently. Wait for the future.
>  
> Regards,
> Michael

Good plan.

Meantime I might try creating another IPv6-only email domain and see
how well it does.  Last I tried (long time ago) it was OK for IETF
work, with IPv4 only people replying about bounces to replies that
went to me plus to the list, but I got the list copy.
12