qmail concurrency problem

[dw604]

When queueing email to a large list of, say, 100,000 messages it works fine for a short time, with up to 250 concurrent qmail-remote processes. After a while the number of qmail-remote processes dwindles down to 10-20 and won't go any higher. My client emails purchased lists and so generates higher-than-average complaints. As a result they are sometimes blocked from connecting to Yahoo or HotMail... could this be part of it? Perhaps these failed connections are "holding" the connection, preventing qmail from starting the next one(s)?

Are there any settings anyone can recommend tweaking? I read something in these forums about an "smtp remote timeout" setting, but can't find it now.

Shutting down qmail, killing all qmail-* processes and restarting seems to work or a short time but it happens again not long after.

Server is FC4 Plesk 7.5.4. concurrencyremote is set to 250, -Rt0 is added to xinetd and qmail is recompiled with conf-split 199.

Thanks for any advice.

 

[dw604]

I have made an strace of the qmail-rspawn process, viewable here

Thanks again for any assistance