Incoming failures.
WHAT TO ESTABLISH
All senders or specific ones? Does webmail show it? When did it stop?
IF WEBMAIL SHOWS IT
Your client is not synchronising, or a filter moved it.
Check all folders, including Spam and Trash.
IF WEBMAIL DOES NOT SHOW IT
Check the mailbox is not full Check MX records point to your mail server Check filters and forwarders Check whether the sender received a bounce
THE FULL MAILBOX POINT
A full mailbox rejects incoming mail.
The sender receives a failure and you receive nothing.
Silent from your side.
THE MX RECORD POINT
If MX records point elsewhere, mail goes there.
Common after a DNS change or migration.
THE FILTER POINT
A filter you or someone else created may be moving or deleting mail.
Check cPanel filters and any client rules.
A RULE YOU DID NOT CREATE
Indicates a compromised account. Change the password immediately.
WHAT TO ASK THE SENDER FOR
The bounce message, if they received one.
