sendmail was reconfigured a few weeks ago to send mail from its queue every 15 minutes instead of every minute. We did this to reduce load on the machine, but the result is that Bugzilla mail is arriving late and out of order. sendmail should be reconfigured to send mail more quickly.
Taking this one.
So far, seems to be working much better. Bugmail is mostly getting received within 5 minutes now, or so it appears. Some of them are even showing them arriving at the destination server 2 or 3 minutes before being received from Bugzilla by mothra. :-) (I think mothra's clock is off a little)
I changed the queue interval from 15 minutes to 5 minutes last night, and I guess it worked, but I'm going to leave this bug open until I get more feedback that this definitively fixes the problem.
As of a few days ago, it takes 5-10 seconds for mail to be sent, and bzbot to process it. In some cases, such as when I marka bug as a dupe of one with lots of people on the cc list, it announces the status change before the page has finished loading for me. I don't know what you did, but I'd say that 8 seconds for mail delivery is an acceptable response time....
Everyone says it works now, and that's because the "sendmailnow" parameter was turned on last week or the week before (but I don't know by who). It seems to have done the trick without any negative side-effects, so I'll leave it on and resolve this bug fixed.