Mail (El Capitan): Mail troubleshooting

Problems sending messages

If you can’t send messages

If people don’t receive your messages

Problems receiving messages

If you can’t receive messages

If messages aren’t displayed or appear incorrect

If junk mail filters aren’t working correctly

Problems viewing messages and mailboxes

If a mailbox is offline

If searching doesn’t find the right messages

If messages aren’t displayed or appear incorrect

If messages appear to be missing

If draft, sent, junk, and deleted messages aren’t where you expect

If your version of Mail doesn’t open

Problems using your email accounts

If an account is inactive

If a mail server rejects your login information

If Mail can’t connect to your email account

Free up storage space for an account

Problems with security

If Mail can’t decrypt messages

If Mail can’t verify a server’s certificate

If Mail can’t verify a signed message