I have an Exchange 2010 Server Environment, we have users in this environment that cannot email an external users primary SMTP email address. All emails to that user ends up in the queue with the following error:
"The mailbox recipient does not have a mailbox database"
However, that external user can receive all emails from all other external/internal email clients, except us.
Troubleshooting done so far:
1. Created an email to multiple recipients in that same external organization as well as others, sent the email and all recipients received the email except this particular user.
- Checked our spam filter, it picked up all recipients and processed their items, however it never received any information for the affected user (as if something was preventing it from even reaching the spam filter)
2. Checked Spam filter = no rules blocking emails for this particular user.
3. They have check their Outlook rules (none), and checked Hub Transport rules (none). No issues here for that users in their environment.
4. Checked our environment under Hub Transport and no rules are here regarding this user.
5. A new alias was created for this affected user in his environment, we then tested by sending him an email and everyone is able to send them an email without issues.
Many thanks in advanced.