[Mimedefang] Telling Mailer to disconnect
Benoit Panizzon
benoit.panizzon at imp.ch
Thu Aug 14 04:30:39 EDT 2014
Am Thursday, 14. August 2014, 10.03:03 schrieben Sie:
> SMTP error code 421 = "Abort connection."
Nope, during the RCPT TO: phase this is a temporary error of just this
recipient. The other (even future recipients) could be valid, so the milter is
getting the remaining recipients until the 'max recipients' limit of the
mailer is reached. But the mailer then also only rejects the additional
recipients with a 'too many recipients' tempfail.
Well postfix somewhen disconnect with 'too many errors' but that limit is even
higher.
The problem with those abusers is that they try to send emails to thausends of
recipients causing some load on the database that I would like to avoid.
What I would like to do is disconnect the client connection during
filter_recipient. I fear this is not possible.
Of course, if $SendmailMacros{auth_authen} points to a phished account that
got 'blocked' in the past, I can reject the connection during filter_sender.
But still this leaves the problems of the recently blocked account. I see bots
opening one connection and then keeping that connection open while trying to
spam. As they got detected during the filter_recipient phase, they cannot send
emails as I reject every recipient. No matter if I use TEMPFAIL or REJECT they
keep trying to send undil they disconnect. Next connection they are blocked
earlier, in filter_sender.
Not all connections get permanently blocked (triggered by simultaneous logins
from many different IP's or different geoIPlocations). If only one IP is
involved I only rate limit the recipients and put up a nagios warning so a
human can determine if this is a bot sending spam or a customer who got the
spledid idea to use our infrastructure as smarthost for his mailing tool. But
still in such a case I would like to disconnect our customer instead of
processing every recipient his tool is trying to send emails to.
Benoit Panizzon
--
I m p r o W a r e A G -
______________________________________________________
Zurlindenstrasse 29 Tel +41 61 826 93 07
CH-4133 Pratteln Fax +41 61 826 93 02
Schweiz Web http://www.imp.ch
______________________________________________________
More information about the MIMEDefang
mailing list