themetman mail user names must be unique across the entire platform, so if you're trying to create a mail user with a name that someone else is already using then you'll receive the "Mail User with this name already exists" error.
You don't need a mail user for a forwarding address. You do need to wait several minutes before any new/modified addresses are propagated throughout the mail system, so please be sure to wait around 10-15 minutes prior to testing a forwarding address. We're working to reduce these propagation delays.
The 24-hour delete queue is a safety net to ensure that you don't inadvertently delete data. If you want to bypass the delete queue then you can click the trash can icon that appears for that mail user (more info at: Deleting Mail Users) - you'll need to do this to clear them all out and start over.
