[lug] Making Postfix Play Nice (I'm not spam, really!)

[Lee Woodworth]

On 07/28/2011 05:37 PM, Ben Luey wrote:
> When sending out e-mails to our mailing list, I'm having a problem with 
> some sites thinking I'm sending spam and blocking my mail server. I'm 
> running postfix and the problem is that many of our subscribers have the 
> same domain / mail server (say example.net). Postfix starts sending the 
> users' mail. After ~10 emails in a row to example.net, example's smtp 
> says "451 4.3.2 Please try again later (in reply to MAIL FROM command))" 
> as a spam blocking protection. That's no problem and  Postfix respects 
> that and tries again later -- for that one email.  But postfix may have 
> 50 more emails to send to that domain, so it tries to send them and gets 
> the same 451. After 10 attempts in one second, example.net gets tired of 
> giving 451 and blocks my mail server.

Search the postfix mailing list archives. I believe this kind of thing has
been discussed there: www.postfix.org.

> 
> Is there a way to get postfix, when it gets a 451 message, to back off 
> sending all emails to that domain? If postfix only tried 2 or 3 times 
> after getting the 451 and then had the whole example.net queue wait 5 
> minutes and try again, I think all would be happy. But instead postfix 
> keeps pounding their mail server with ~50 requests in row that all get 
> 451. Then in 5 minutes, it tries all 50 requests again. Then in 5 
> minutes it tries 50 requests again. Then it waits 10 minutes and tries 
> again, but after the delay,cycle postfix tries EVERY email to that 
> domain in just a few seconds. I've backed off the number concurrent 
> connections max to 5 and that didn't make a different -- I think it 
> isn't the concurrent but consecutive connections.
> 
> Ideas?
> 
> Ben
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