Hi Sam and list,

just thought, I´ld give you some feedback on what worked finally.

We had the strange situation that the smtp ports just got plugged and it was 
partially impossible for customers to open a connect for sending mails ... and 
of course for other mailservers to deliver to ours.

Bad situation on a production system (problems like that never occured in 
testing env.)

I tried about everything I could configure with spamdyke and other progs to get 
the problem solved ... I even took all ips from the logfile that had 
DENIED_RDNS entries and dropped them on kernel basis to get ride of connections 
and free smtp again ... Only worked for a moment.

BTW, there is a ratio of 16:1 in DENIED_RDNS, meaning on a daily basis ips with 
no rdns mad on naverage 16 attemps to connect.

Anyway, /var/log/qmail/smtpd/current showed a total of no more than 200 
connections, our maxconcurrency was set to 1024 - so obviously enough romm .....

Wrong.

Thats 200 qmail-smtpd connections ... and when for each qmail-smtpd connect you 
have a ton of spamdyke dns tests and other connects ... that means that 
tcpserver has reached its 1024 limit, even if current only shows 200 
qmail-smtpds.

I raised maxconcurrency to 8192 and guess what ... load on the mailservesr 
reached the normal level again, since all incoming connections are working 
again. 

So, not exactly a bug, but something which might be a nice addon: Logging the 
connects of spamdyke - maybe in addition to the qmail-smtpd connects, so you 
have control over active connections compared to maxconcurrency.

This would have saved me quiet some trouble with pretty angry customers.
Maybe somebody more sophisticated than me is able to patch tcpserver itself to 
produce such an outpiut in a logfile ...

------------------------------------

And a hand shell line, to find out, who is producing the connections:
for i in `cat /var/qmail/control/morercpthosts`; do echo -n $i >> /root/mails 
&& cat /var/log/mail.log.0 | grep $i | wc -l >> /root/mails; done

This produces a nice list of logentries per domain per day (depending on your 
logrotate).


Thanks for reading - u.


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