handling spam from gmail.

[Andreas Born]

Am 12.06.2020 um 04:43 schrieb Adi Pircalabu:

> First thing first, this isn't necessary a Dovecot related thread and 

yeah, and i'm sorry for that. Just thought to give some information on 
an issue that actually turns out to be completely out-dated.

> using a challenge-response system like the one suggested by the 
> initiator ("click here if you're not yet another bloody SEO guru") is 
> plain wrong for several reasons, 

full ack

> $ telnet server 25
> Trying x.x.x.x...
> Connected to server
> Escape character is '^]'.
> 220-server ESMTP Postfix <=== Postscreen trap here ;)
> 220 server ESMTP Postfix
> HELO client.domain.com
> 250 server
> MAIL FROM:<>
> 250 2.1.0 Ok
> RCPT TO:<victim at domain.com>
> 250 2.1.5 Ok
> DATA
> 354 End data with <CR><LF>.<CR><LF>
> From: Me
> To: You
> Subject: Test
> 
> SA GTube string here
> .
> 550 5.7.1 Blocked, see you later.
> QUIT
> 221 2.0.0 Bye
> Connection closed by foreign host.
> 
> In this case the rejection comes after DATA, a content filter should be 
> able to return either 4xx or 5xx *after* swallowing the entire email.

I know and I already tried out such a filtering long before. With lots 
of problems and long discussions to mailadmins of large providers. The 
result: specifications and reality do not always match. :-)

>> Maybe, and I really hope so, this problem no longer exists. I will
>> immediately reconfigure my mail system, if rejecting mails after DATA
>> will be safe and reliable nowadays.
> 
> Rejecting or deferring after DATA is perfectly fine these days. If the 
> sending MTA, acting as a client in the SMTP conversation, doesn't behave 
> properly to 5xx after DATA, it's not the recipient's MTA problem, the 
> sender is broken and there's nothing the receiving MTA can do about it. 
> Make it their problem, not yours.

Okay, makes sense!


/ Andreas