Questions regarding Backup MX and Postfix's Queue.

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Questions regarding Backup MX and Postfix's Queue.

dusty - linuxgeek
Hi guys,

I have a couple of quick questions:

1) How long does a message sit in the postfix queue for before it attempts
a redeliver (a deffered message sat in the deffered queue)?

2) If you have a mailserver (postfix, dovecot, virtual users/domains mysql)
and you have a back-up MX record set if the main mailserver goes down
(reboot) and a mail gets sent to a domain hosted on the server, it gets no
response from the main mailserver so reverts to the backup.  It delivers
the mail to the backup and then defers it because it cannot be sent to the
main mailserver, it then sits in the deferred queue until the main
mailserver is back and gets delivered.  wonderfull... the question is, if
the server is down due to a reboot for whatever reason so say 5 - 10 minute
downtime.  The original message will be sent, goto the backup mx, it will
get deferred until mailserver is backup then delivered... BUT I tested this
with hotmail, and what I get is, hotmail defers the message as well as
sending it to the backup mx, so that when the backup mx delivers the mail
which goes through fine, hotmail are retrying as well, and you end up with
two of the same message? How do you overcome this?

Kind Regards,

Dusty.
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Re: Questions regarding Backup MX and Postfix's Queue.

Wietse Venema
[hidden email]:
>
> I have a couple of quick questions:
>
> 1) How long does a message sit in the postfix queue for before it attempts
> a redeliver (a deffered message sat in the deffered queue)?

http:/www.postfix.org/postconf.5.html#queue_run_delay
http:/www.postfix.org/postconf.5.html#maximal_backoff_time
http:/www.postfix.org/postconf.5.html#minimal_backoff_time
http:/www.postfix.org/postconf.5.html#maximal_queue_lifetime

> with hotmail, and what I get is, hotmail defers the message as well as
> sending it to the backup mx, so that when the backup mx delivers the mail
> which goes through fine, hotmail are retrying as well, and you end up with
> two of the same message? How do you overcome this?

If hotmail sends the same message to the backup and to the primary
MX, then there is nothing that Postfix can do about it.

        Wietse
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Re: Questions regarding Backup MX and Postfix's Queue.

@lbutlr
In reply to this post by dusty - linuxgeek
On Mar 5, 2009, at 7:33, <[hidden email]> wrote:

> Hi guys,
>
> I have a couple of quick questions:
>
> 1) How long does a message sit in the postfix queue for before it  
> attempts
> a redeliver (a deffered message sat in the deffered queue)?
>
> 2) If you have a mailserver (postfix, dovecot, virtual users/domains  
> mysql)
> and you have a back-up MX record set if the main mailserver goes down
> (reboot) and a mail gets sent to a domain hosted on the server, it  
> gets no
> response from the main mailserver so reverts to the backup.  It  
> delivers
> the mail to the backup and then defers it

Your backup MX is deferring the message? As far as the sender is  
concerned, once the message is accepted by your server, it should be  
considered delivered, no?

> because it cannot be sent to the
> main mailserver, it then sits in the deferred queue until the main
> mailserver is back and gets delivered.  wonderfull... the question  
> is, if
> the server is down due to a reboot for whatever reason so say 5 - 10  
> minute
> downtime.  The original message will be sent, goto the backup mx, it  
> will
> get deferred until mailserver is backup then delivered... BUT I  
> tested this
> with hotmail, and what I get is, hotmail defers the message as well as
> sending it to the backup mx, so that when the backup mx delivers the  
> mail
> which goes through fine, hotmail are retrying as well, and you end  
> up with
> two of the same message? How do you overcome this?

Um, hosts.deny hotmail? ;)

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Re: Questions regarding Backup MX and Postfix's Queue.

dusty - linuxgeek
In reply to this post by Wietse Venema
Wietse Venema wrote:

> [hidden email]:
>  
>> I have a couple of quick questions:
>>
>> 1) How long does a message sit in the postfix queue for before it attempts
>> a redeliver (a deffered message sat in the deffered queue)?
>>    
>
> http:/www.postfix.org/postconf.5.html#queue_run_delay
> http:/www.postfix.org/postconf.5.html#maximal_backoff_time
> http:/www.postfix.org/postconf.5.html#minimal_backoff_time
> http:/www.postfix.org/postconf.5.html#maximal_queue_lifetime
>
>  
>> with hotmail, and what I get is, hotmail defers the message as well as
>> sending it to the backup mx, so that when the backup mx delivers the mail
>> which goes through fine, hotmail are retrying as well, and you end up with
>> two of the same message? How do you overcome this?
>>    
>
> If hotmail sends the same message to the backup and to the primary
> MX, then there is nothing that Postfix can do about it.
>
> Wietse
>  

Thank you Wietse.

Dusty.