There is an intermittent problem with the way digest mails are sent out.

From time to time 10 or so identical digest mails will be sent to the same user.

It is not always the same user, nor the same course.

All mails are sent at the same time.

I am afraid I cannot give more detail on this, mails are sent out overnight and I cannot find any relevant information in the logs.

I am as sure as I can be that this is not an error within the mail server.