I deleted a user account, "firstname.lastname@example.org". Since, I removed said account, everyone who emails "email@example.com" is receiving a bounce back which indicates a delivery failure:
Failed Recipient: firstname.lastname@example.org
Reason: The recipient does not exist
email@example.com is not listed as a forwarding address for firstname.lastname@example.org, nor is it associated with any groups. I've looked through just about everything in the admin panel... anyone have any ideas?