Are the new aliases you created forwarding to a Gmail account? Also, are you sending test messages from the Gmail account to which the mailmap is forwarding?
Some mail hosts won't deliver emails sent from their system, which forward back from another. The best way to test is to make sure the email address you're sending from isn't the target address of the mailmap.
One forwards to both a Gmail and an outlook.com address. Both of these destinations are already used individually in other mailmaps that work. The other I made just as at test - it forwards to the same outlook.com address that is my own main personal address. I've tried sending from Office 365, Outlook.com and an old CompuServe address - so far nothing has got through and (so far) there have been no returned NDRs either.