@Appletech The large figure on the Campaigns page is the number of attempts to send so I guess that you had a very large number of errors when sending. Possibly the send rate is too high.
Look at the event log page to see if anything has been reported there.
Our phplist application is on a web server connecting to the mail server on port 587 using TLS in order to submit mails. If I understand your comments right, then the phplist application on the web server tries too often to connect and these connections fail.
@Appletech The config.php settings that you showed will send 300 emails at 1s intervals, so 300 emails in about 400s, which is much more than you are allowed.
Domain throttle will slow that down but it looks like the rate is still too fast. You need to change the batch size and batch period to meet the restriction.
The event log messages are caused by you having VERBOSE enabled in config.php. You should turn that off as the volume of event log messages swamps other more important messages.
@Appletech In the development version of phpList (which will become phpList 3.3.2) the stats are labelled differently, partly in order to clarify what you describe. The table containing the confusing statistic is now titled ‘Processed’ (because processing attempts are not the same as messages sent). See screenshot.