I have a domain mycompany.com and I created an alias myoldcompany.com.
When I send mail to firstname.lastname@example.org, it bounces:
This is the mail system at host mail.mycompany.com.
I'm sorry to have to inform you that your message could not
be delivered to one or more recipients. It's attached below.
For further assistance, please send mail to postmaster.
If you do so, please include this problem report. You can
delete your own text from the attached returned message.
The mail system
<email@example.com>: User unknown in virtual alias table
As a test, I added an alias to firstname.lastname@example.org to be email@example.com and it worked. However, I've never had to do this before.
Any ideas on what's going on here?