A common question from new Exchange administrators, especially those who moved from other email systems, is “Does Exchange have a catch-all email option?” I’m seeing this question more frequently as small companies and individuals move to Office 365’s Exchange Online.
If someone misspells my name, I don’t want the sender to receive an NDR. I want the message delivered to my Exchange mailbox.
Exchange Online does not offer a catch-all mail option. This is because the Exchange Online anti-spam filters use recipient filtering to reject messages sent to mailboxes that don't exist.
While not supported by Microsoft, you can change your Exchange online configuration to accept all mail to the domain, then use a mail flow rule to redirect the mail to a "Catch All" mailbox. Instructions are at Configure Catch all Mailbox in Microsoft 365 - o365info
While you can disable recipient filtering to make it work in an on premises server, I don’t recommend it as it’s basically a spam magnet. When users leave, or if someone’s address is frequently misspelled, you can receive mail for the addresses by adding the address to a mailbox. The messages sent to the address will be delivered and all replies will be sent from the mailbox’s default SMTP address. For example, I can receive mail sent to dianne@ but reply using my "real" email address. I can also have a mailbox for sales@, and accept mail for help@, info@ and other common generic addresses.
If you prefer, you can add the addresses to distribution groups in the GAL and make the correct mailbox the DL’s sole member. The benefit of using a DL is that users can be given SendAs permission and the address used as a reply address.
Tip: If you need to capture all addresses currently delivered to a catchall mailbox, you can use a macro to create a list. Then use PowerShell to add the addresses to a mailbox.
