Below are suggested steps to troubleshoot why your email account is not showing up when you search for it in the address book.

1. Check the email address in the address book and confirm it is correct.
2. If it is correct, try a mailbox rebuild.
3. Check the email filtering by going to Preferences > Filtering
4. If these steps have not solved the issue, it may be related to a corrupted address book. Try repairing or rebuilding the address book file.