Take the tour ×  I'm writing an email notification system that
needs to send many hundreds of emails at once. The system needs
to be deployed on various setups with different MTAs. Depending
on the configuration, some MTAs seem to receive an email from an
application and queue it as fast as possible; others will hold
the sender application while processing (sending?) the message –
this would cause the application to block for extended periods
of time.  Would it be reasonable to expect MTAs on production
machines with modern software to queue mail quickly (or be
configured to do so)?  share|improve this question add comment
2 Answers  Unfortunately, it depends. If you need to work with a
variety of different MTAs, then you're going to have to do
things like load average detection (if the load average rises
above a certain number, then throttle delivery), and probably
also do your own domain aggregation to reduce the number of
delivery attempts required.  share|improve this answer I'd leave
all that to the MTA