1) Low traffic mail server will have this issue, because MySQL connection (open by Amavisd) timed out.
2) Restarting MySQL service will cause the same issue, because existing MySQL connection (open by Amavisd) cannot connect MySQL server.

To fix 1), please try set below settings in Amavisd config file (http://www.iredmail.com/docs/file.locat … ml#amavisd):

$max_servers = 1;
$max_requests = 1;

Hey Zhang. I made the changes that you specified, and all throughout last night, and today, I didn't receive any disconnect notices in my log files. It appears that it was related to the "mysql has gone away" error, but instead related to amavis timing out instead of mysql, as mysql seems to continue to run, even though Amavis seemed to die. I did receive a notice in my logwatch report this morning that said:

4   *Warning: Virus scanner timeout
4   Miscellaneous warnings

as well as:

55   Connections             
        9   Connections lost (inbound)
       55   Disconnections         
       37   Removed from queue     
       15   Delivered               
       19   Sent via SMTP           
        3   Forwarded               
        2   Deferred               
        4   Deferrals

The lost connections are related to Suricata working in IPS mode on the machine, and filtering out generic SMTP decode commands. However, I believe that the deferrals, as well as the Amavis timeouts to be from before I had made the changes, as since I have made the changes, I haven't noticed any disruptions, or deferrals.

One question: Since we have a mailing list of approximately 1,500 subscribers for our record label, with these changes to Amavis, will I notice any performance degradation when sending out to our mailing list, if I try to send to all 1,500+ subscribers? Should I return the server back to the original 4 Amavis servers setting before an email blast goes out? I'm just wondering if this is something that I'm going to have to change back before we send out an email blast to our mailing list? Just curious. I'm still keeping an eye on this issue, but so far, so good. I'd love to hear your thoughts on the performance if we send out an email blast to our mailing list with the current settings...

Many thanks!

Hey Zhang! Thanks so much for the reply. This morning's logwatch showed no errors, and I'm looking through the log files this morning, and noticing nothing out of the ordinary. No disconnects, no Antivirus alerts, and no Amavis errors. It's been up for almost 2 days now with no noticeable disconnects that I can see. To answer your question, I'm running 2gb of RAM on this machine, with about 200mb free RAM most of the time, with everything running on it. Yes, ClamAV is running on this machine as well. It's been running ClamAV updates and restarting the service as normally. I'm hoping that the issue is fixed, now. Thank you so much for advising me, and helping with this issue. I'll keep monitoring the issue for the next couple of days. Hopefully all remains good! Thank you!

Hey Mir! Yes, I'm running clamd. I haven't modified any of the ClamAV settings from the initial iRedMail setup, from when I put this machine together with 0.9.2. It appears that there is only one instance of clamd running on this machine. I believe that the antivirus warnings were related to Amavis, not ClamAV (I was under the impression that Amavis launched ClamAV when it's needed, anyway, right?).

I'm also getting this error:

Aug 13 20:09:06 mail amavis[5959]: (05959-01) (!)rw_loop: leaving rw loop, no progress, last event (select) 35.040 s ago

Please help if someone can!

If you need to post log, please post log context also. otherwise it's hard to help troubleshoot.