Mail App on Mac Not Receiving Email — Fix Guide
Apple Mail stops working in a small number of predictable ways. Here's how to walk through them.
Confirm the problem is Mail and not the account. Log into the same email address through a web browser. If new messages arrive there, the server is fine and the issue is local to your Mac.
In Mail, choose Mailbox, Take All Accounts Online and then Mailbox, Synchronize. Sometimes that's all it takes. If a specific account has a warning triangle next to it, click it for the actual error.
Connection Doctor under the Window menu is the underused tool here. It tests every account and tells you exactly which server is failing and why. Most issues turn out to be expired app-specific passwords for Gmail or Yahoo, both of which require them now for Mail to authenticate.
If Connection Doctor shows green across the board but Mail still misbehaves, rebuild the mailbox — Mailbox menu, Rebuild. It can take a while on big mailboxes but usually resolves index corruption.
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