Email delivery fails on postfix on heavy load

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Email delivery fails on postfix on heavy load

Sharma, Ashish-2
Hi,

I have a postfix(postfix 2.6.5) mail receiving server.

On this I have used an email filter (sendmail-jilter http://sendmail-jilter.sourceforge.net/) that have some of my custom code. Following setting is used for the milter in 'main.cf':

#Milter support for smtpd mail
smtpd_milters =
  inet:localhost:10028

milter_protocol = 2

Here on email loads of approx 40/hour the setup is fine but for email loads of approx 600/hour, I am facing following messages in postfix logs:

Aug  9 07:34:12 ip-10-244-155-191 postfix/cleanup[10308]: warning: milter inet:localhost:10028: can't read SMFIC_EOH reply packet header: Success
Aug  9 07:34:12 ip-10-244-155-191 postfix/cleanup[10308]: 771CB100168: milter-reject: END-OF-MESSAGE from xxx.atlanta.xx.com[15.xxx.32.xx]: 5.5.0 Service unavailable; from=<xxxx.xxxx@**.com> to=<[hidden email]> proto=ESMTP helo=<xxx.atlanta.xx.com>

On checking the milter side logs I can see that mail is getting passed successfully but because of above logged problem the email sender server gives out

'550 5.5.0 Service unavailable'

in the inbox of mail sender.

Any idea what's going on?

Please help!!!

Thanks in advance
Ashish Sharma
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Re: Email delivery fails on postfix on heavy load

Wietse Venema
Sharma, Ashish:

> Hi,
>
> I have a postfix(postfix 2.6.5) mail receiving server.
>
> On this I have used an email filter (sendmail-jilter http://sendmail-jilter.sourceforge.net/) that have some of my custom code. Following setting is used for the milter in 'main.cf':
>
> #Milter support for smtpd mail
> smtpd_milters =
>   inet:localhost:10028
>
> milter_protocol = 2
>
> Here on email loads of approx 40/hour the setup is fine but for email loads of approx 600/hour, I am facing following messages in postfix logs:
>
> Aug  9 07:34:12 ip-10-244-155-191 postfix/cleanup[10308]: warning: milter inet:localhost:10028: can't read SMFIC_EOH reply packet header: Success
> Aug  9 07:34:12 ip-10-244-155-191 postfix/cleanup[10308]: 771CB100168: milter-reject: END-OF-MESSAGE from xxx.atlanta.xx.com[15.xxx.32.xx]: 5.5.0 Service unavailable; from=<xxxx.xxxx@**.com> to=<[hidden email]> proto=ESMTP helo=<xxx.atlanta.xx.com>

Have you configured "milter_default_action = reject"? Don't do that
if you want mail to be tried again latrer.

Unfortunately, Milter applications can fail under high load - they
run inside one multi-threaded process, while Postfix runs one smtpd
process and one cleanup process per SMTP session.

        Wietse