Two days ago, I began using SpamTitan Cloud for my spam filtering. I am running a trial (30 day). Because of that, my outbound email is still going through the old spam service (ST does not support outbound until after the trial). Everything seemed fine until this morning. Email is reaching my Exchange 2016 server but is not progressing beyond the Submission queue. Outbound email is also being held up in this queue.
The queue is showing errors such as "Message deferred by categorizer agent" and "[{LED=400 4.4.7 Message delayed}...].
Is the problem related to my config with SpamTitan or is it something internal? Waht should I be looking at. I have tried reboots and stop/starting MSExch Transport.