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What sucks is qrunner just tries to deliver each message one at a time. If message 5 takes forever on the rcpt to: command (for example), no other messages deliveries are attempted because qrunner sits on message 5 until it times out.

Translation: You are doing name lookups on messages delivered via SMTP from the localhost. There's not much reason for this. Turn it off.

Just out of curiosity: anyone know how to do this in sendmail?

Is this the 'delay_checks' feature?

I'm sure I haven't configured it, but my list isn't big enough that I care about such delays. If I were to want to change it, though, it's not at all clear to me how I would, and since it's become such a refrain....anyone know?