We've noticed that some of the emails that ISM is trying to send aren't going through. Specifically, we have a number of emails that are sitting in the Draft folder of the Exchange mailbox it uses. It looks like ISM created the messages as it should, but they never sent. We can see messages being sent. They briefly pop into Drafts if you watch the mailbox with an Outlook client, and then disappear, then appear in Sent folder like normal. But a few messages per day just pop into Drafts and never leave. There are no records of it in the Sent folder. The log in ISM shows that the messages are sent, and without any errors.
We've tried to find a pattern to the emails that fail. Are they all from the same business object, rule, or action? Is it to specific users, at certain times of day, etc? Unfortunately, it's all over the map. Some are survey emails after an incident is closed. Some are notifications to end-users that a new incident was created. Some are team notifications telling them they have a new assignment. It happens during peak hours and even on the weekends.
Anyone ever seen anything like this before?