Tweak Postfix so that it will resend emails after the initial 451 response

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Tweak Postfix so that it will resend emails after the initial 451 response

jan gestre-3
Hi Guys,

I have a Postfix server behind a gateway firewall that does content
filtering (SpamD on pfSense) and greylisting and we have an
application server that uses Postfix as its MTA, the problem is after
the initial 451 response the latter quits and send an Undeliverable
Mail to sender, what changes needs to be done on the latter in order
for it to resend email successfully, I don't have a problem with other
third party mail server except for this one. Since I don't have access
to the latter I can't provide any logs except for the following:

---
This is the Postfix program at host mail.latter.sample.

I'm sorry to have to inform you that the message returned
below could not be delivered to one or more destinations.

For further assistance, please send mail to <postmaster>

If you do so, please include this problem report. You can
delete your own text from the message returned below.

   The Postfix program

<[hidden email]>: host webmail.former.sample[210.21x.xx.xx] said:
    451 Temporary failure, please try again later. (in reply to DATA command)

----

TIA.
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Re: Tweak Postfix so that it will resend emails after the initial 451 response

Barney Desmond
2009/11/23 jan gestre <[hidden email]>:

> I have a Postfix server behind a gateway firewall that does content
> filtering (SpamD on pfSense) and greylisting and we have an
> application server that uses Postfix as its MTA, the problem is after
> the initial 451 response the latter quits and send an Undeliverable
> Mail to sender, what changes needs to be done on the latter in order
> for it to resend email successfully, I don't have a problem with other
> third party mail server except for this one. Since I don't have access
> to the latter I can't provide any logs except for the following:
>
> ---
> This is the Postfix program at host mail.latter.sample.
>
> I'm sorry to have to inform you that the message returned
> below could not be delivered to one or more destinations.
>
> For further assistance, please send mail to <postmaster>
>
> If you do so, please include this problem report. You can
> delete your own text from the message returned below.
>
>   The Postfix program
>
> <[hidden email]>: host webmail.former.sample[210.21x.xx.xx] said:
>    451 Temporary failure, please try again later. (in reply to DATA command)

It sounds like your application server isn't doing the right thing.
The 451 error code indicates a temporary error, and that the sender
should try again later. If it doesn't retry, that is the sender's
fault, it's not following the spec.

The best solution is to fix the sender. An alternative would be to
whitelist the sender on the Postfix box. As you say, you don't have
access, perhaps you can try contacting whoever administers the server.
Greylisting is an anti-spam measure (ie. "incoming" mail). Your mail
sounds like it's outgoing, so it shouldn't be unreasonable to get
whitelisted.
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Re: Tweak Postfix so that it will resend emails after the initial 451 response

Wietse Venema
In reply to this post by jan gestre-3
jan gestre:
> <[hidden email]>: host webmail.former.sample[210.21x.xx.xx] said:
>     451 Temporary failure, please try again later. (in reply to DATA command)

Postfix always resends after 451, but it stops when the message
is too old (the default limits are: maximal_queue_lifetime = 5d
and bounce_queue_lifetime = 5d).

The maillog file will show how long Postfix has been retrying
deliveries.

        Wietse