Hanno Hecker wrote: > [Answer also to ML] > > On Tue, 15 Jan 2008 21:23:46 +0100 > "David Bouw" <[EMAIL PROTECTED]> wrote: > >> The only thing that makes me curious is that the sender's mailer will have >> to keep waiting for a response (code) till the mail has been completely >> forwarded: > [...] >> Isn't there any risks of the senders mailer timing out waiting for the >> smtp-forward to complete. ? > Yes, that may happen if the connection is too slow for the size of the > message. In that case the recipient can get it into it's Inbox (even > more than one copy of the message, if it times out several times) but > the sender still thinks it has not been delivered.
Having had experience with an high volume production system that can behave similarly for the past 10 years ... It's usually not an issue. It's all going to depend on what level of timeliness you can expect between the client sending the final ".", post "." processing in qpsmtpd, how long the output server tends to take and how impatient your clients are. With Mailshield (mostly implemented in Perl like qpsmtpd) under the following conditions: - volumes approaching 1.5M/day across 5 servers, mail size average rather larger than "common" - Mailshield performing most of its tests (including SpamAssassin and explicit body string scans with regexps) after ".". We only get "client times out, but recipient did get it, resulting in duplicates" during periods when either a significant fraction of the mailshields were down (hence whole thing funneled through 1 or 2 servers), or when we had severe networking problems internally - eg: extraordinarily long DNS delays, or router misrouting causing either the mailshields or the inwards servers to bog down. We've had occurrences of this less than 10 times in 10 years, and the sheer quantity of problems is quite low. A handful of reports each time. That said, we had to hack Mailshield to do full body scans only on emails under a certain threshold size, otherwise, they'd go into overload. About 60K. We do limited body scans on emails larger than that. For our new qpsmtpd filter implementation, I'm going to be putting intelligent failover into the forwarding agent. But I'm going to avoid queuing - I like the quality of having the servers vaporizable without loss of email.
