Why does sending mail through the Outbound Mail service seem slow?
We do scanning and filtering a bit different than everyone else: we do it in real time (or as close to it as possible). This means that when you submit a message through our outbound mail service the submission restrictions are being applied before we’ll return an “accept” or “reject” response at the cost of a few extra seconds of processing time. This slight acceptance delay has no bearing on the actual delivery to the intended recipient. The same process is applied to incoming mail, but due to the non-interactive nature of MTA-to-MTA communications, it goes unnoticed.
