OS X El Capitan fix: can’t send email after upgrade

System Preferences showing iCloud Mail**Update 21 Oct 2015: Apple released OS X 10.11.1 which claims to have fixed this problem**

After upgrading many Macs to OS X 10.11 El Capitan, I’m finding a bug that seems to be quite consistent. Virtually everyone who uses an email address ending in @me.com is suddenly unable to send messages using the built-in Mac Mail program. Emails still come in but the outgoing messages don’t go. Fortunately it’s a very quick and easy fix.

  1. Disable and re-enable your iCloud email.

    • Go to the Apple menu > System Preferences > iCloud (3rd row).
    • Click the checkbox next to Mail to disable it.
    • After waiting for the checkmark to disappear, click the box to turn Mail back on.
    • You can close the System Preferences window.
  2. Outgoing email serverSet your outgoing email server.
    • Open Mail.
    • Click the “Mail” menu and choose “Preferences”.
    • Switch to the “Accounts” tab.
    • Choose your iCloud account from the left column.
    • Look for “Outgoing Mail Server” on the right and switch it to “iCloud”.
    • Close the Preferences window to return to Mail.

That should do it! If you have a lot of email in your iCloud account or a slow connection you may need to wait some time for your email to re-download, so don’t worry if your email inbox is empty for a few minutes.