Email not receiving: how to check MX, mailbox and filtering
Incoming mail follows the domain’s MX route to a receiving service and then through mailbox or filtering rules. Troubleshoot from public DNS toward the final mailbox so you do not change a user’s mail client when messages never reached the provider.
Confirm the domain and MX answer from public DNS
Verify the domain is active, authoritative DNS is healthy, and the MX records match the current mail provider. If MX still points to an old service after a migration, the new mailbox cannot receive those messages.
Check whether the receiving service knows the address
Confirm the mailbox, alias, group, or routing rule exists and is not suspended. A typo in the local part can create a recipient-unknown bounce before any user-level spam filtering occurs.
Check quota and filtering after acceptance
A full mailbox, quarantine, spam rule, forwarding loop, or server-side filter can make mail appear missing even though the provider accepted it. Search webmail and server-side folders before blaming a desktop client.
Ask the sender for the bounce when one exists
The SMTP response often identifies the failed layer: unknown recipient, temporary deferral, policy rejection, DNS failure, or another reason. The exact code is more useful than “it bounced.”