We are having problems with the performance using the queue delivery mode. When I run the Email_Messages query, it returns a lot of records in "Ready" state. If I restart the service, then finally those records get the "Delivered" state. The execution interval of the service has been set to 3 minutes. This delay affects the end user's work. Some of those mails are lasting until 1 hour to be delivered.
What can we do to improve the service's performance and avoid the need of restarting it?
Thanks in advance.