Stuart Henderson wrote:
> RFC2821 6.1 - also see 3.7, 4.5.5:
>
> If there is a delivery failure after acceptance of a message, the
> receiver-SMTP MUST formulate and mail a notification message. This
> notification MUST be sent using a null ("<>") reverse path in the
> envelope.
>
> -> do not drop these.
You and Mr. Dempsky make an excellent point, thanks! I re-read my config
file for Postfix and my manual, and noticed my confusion -- I read too
much into rejecting non-FQDN senders, including null in my mind to that
list, but I see my oversight now.
> But try not to generate these notification messages by email. Teaching
> your backup MXes which usernames are valid and which aren't avoids many
> of these. This reduces backscatter, avoid filling your queues with spam
> related bounces to failing addresses, and you avoid a possible method
> to bypass greylisting.
>
> smtp-vilter can handle this too (it has 'reactions' which add addresses
> to PF tables for a certain length of time), I use it with both Sendmail
> and Postfix.
>
Thanks for the tip! I'm looking into smtp-vilter now. I've not come from
a Sendmail background, and my Postfix experience started before milter
support was included in 2.3, so I had largely ignored milter's as an
option. Marc's work looks very intriguing, and PF integration is a great
draw.
Thanks everyone for the input; I think I'm safe for now, but just wanted
to ensure I was staying on top of recent log trends.
- Seth
