[Rspamd-Users] rspamd not handling pause / multi-line 220- in SMTP exchange

Brielle bruns at 2mbit.com
Mon Sep 20 20:30:13 UTC 2021


Discovered a slight issue with rspamd's dmarc_report feature, getting 
following errors:

Couldn't send mail for inmoment.com: bad smtp responce on stage rcpt: 
"220-" when "3" expected

When checking exim's logs...

2021-09-20 14:19:05 SMTP protocol synchronization error (next input sent 
too soon: pipelining was not advertised): rejected "HELO 
mail.xxxxxx.org" H=localhost [] U=root next input="MAIL FROM: 
<dmarc_reports at xxxxxxxxxx>\r\nRCPT TO: 
<dmarc-reports at xxxxxxxxxxxx\r\nRCPT TO: 
<xxxxxxxxxxxxx at xxxxxxxxxxxxxx>\r\nDATA\r\n"

My SMTP server adds a momentary delay before spitting out a multi line 
220 banner (using 220-) which is designed to mess with spambots that 
don't bother to implement proper RFC compliance.

Looks like the report feature either doesn't wait for the final 220 
before sending the HELO, or doesn't recognize that 220- means multi line 
(see RFC 2821 sec 3.1) and just starts trying to send commands right away.

So, not sure if its the initial delay that's causing the problem or the 
220 handling.

Brielle Bruns
The Summit Open Source Development Group
http://www.sosdg.org    /     http://www.ahbl.org

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