[SalesForce] Time dependent workflow email alert is not received

The way you need to approach this is make it so that the workflow always fires, but if the Case is not overdue at the time the Time-Dependent action takes place, the email won't go out. In a deadline scenario, there are usually two factors - the deadline, and some indication of whether the task has been completed. With a Case, this is likely whether or not the Case has been Closed. So your WFR criteria could be:

NOT(ISBLANK(Due_Date__c)) && NOT(IsClosed)

Then your time dependent action would be 0 hours after Due_Date_c. If the Case is closed between the time the workflow initially fires and the Due Date, then the email won't go out. If the case is still open, then the queued email will be sent. If the Due Date is changed, then the workflow re-fires and the old email is removed from the queue and a new one based on the new date is queued up.

Here is what you describe:

1. You have a workflow with time-based email actions
2. The actions go into the queue
3. The actions are then removed from the queue but the email is not sent

If this is, in fact, the case, then this is a bug and should be reported as a case to support.

But in your notes, it sounds like maybe the emails are being sent, you just don't see them logged as activities. Is that actually what is happening?

If so, this is a known behavior (and currently the way this feature works). Take a look at this KB article in online help. In it, you will see the explanation, along with:

1. A suggested work around to also log a task as a second action on the same time trigger.
2. A link to the IdeaExchange idea that you can vote for to make this feature part of the platform.