We have an error sending an Email marketing campaign to 5000+ users. Some mails are sent and some others are not sent.
The task is timed out, and in Monitoring appear and error for each mail not sent:
The only information about this "MergeAndDeliver failed" error inthe forum is at this post, biut it has a different cause (An item with the same key has already been added)
Does somebody know the cause of this error and how to fix it?