If you can’t send an email in the Mail app, because the compose window disappears and reappears

When you attempt to send a message in Mail on your Mac, the message window might disappear and reappear quickly and repeatedly, without sending.

This solution requires removing a few files, so it's a good idea to back up up your Mac first.

Remove the application state files

  1. Quit Mail. If necessary, force it to quit.
  2. From the Finder menu bar, choose Go > Go to Folder.
  3. Paste or type this path as one line into the Go to Folder field, then press Return:

    ~/Library/Containers/com.apple.mail/Data/Library/Saved Application State/com.apple.mail.savedState

  4. The com.apple.mail.savedState folder opens. Drag all of the files in that folder to the Trash.
  5. Restart your Mac.

If this is your first time completing the steps in this section, open Mail again and try to send another email message.

Remove the outbox.mbox files

If the previous steps didn't resolve the issue, follow these additional steps.

  1. Quit Mail. If necessary, force it to quit.
  2. From the Finder menu bar, choose Go > Go to Folder.
  3. Paste or type this path into the Go to Folder field, then press Return:

    ~/Library/Mail/V3

  4. The V3 folder opens. Type outbox.mbox in the search field in the corner of the window, then press Return.
  5. Your search results will likely be empty. Between the search field and the search results, you should see the word Search, followed by options to limit search to This Mac, "V3," and Shared. Click "V3."
  6. You should now see at least one file named outbox.mbox in the search results. Drag all files with this name to the Trash.
  7. Restart your Mac, then open Mail again and try to send another email message.

Remove the SMTP server name and add it back

If the previous steps didn't resolve the issue, follow these additional steps.

  1. Remove the application state files and restart, as described in the first section, but don't try to send another message yet.
  2. Enter your email address in the Mail Settings Lookup tool. If the tool doesn't know your email provider, contact your email provider and get the outgoing mail server (SMTP) settings for your account.
  3. Open Mail, then choose Mail > Preferences. Click Accounts, then select your email account from the list of accounts.
  4. From the Outgoing Mail Server (SMTP) pop-up menu, choose Edit SMTP Server List. A list of servers opens, and the server associated with your email account should already be selected.
  5. Click the Remove button (–) to remove the selected server.
  6. Click the Add button (+) to add an SMTP server. Use the outgoing mail server information from step 2 to complete the Server Name field. This is the server hostname of your outgoing mail server.
  7. Click OK, then close the Mail preferences window and save the changes.
  8. Try to send another email message.

Reset permissions on your home folder

If the previous steps didn't resolve the issue, follow these final steps.

  1. Quit Mail. If necessary, force it to quit.
  2. From the Finder menu bar, choose Go > Home. Your home folder opens.
  3. Choose File > Get Info. An Info window for your home folder opens.
  4. If the “Sharing & Permissions” section at the bottom of the window isn't open, click the triangle in that section to open it.
  5. If the Lock button in the lower-right corner of the window shows a closed lock, click the button, then enter your administrator name and password. 
  6. Click the Action menu in the lower-left corner of the window, then choose “Apply to enclosed items.” Click OK to confirm the action.
  7. When the progress bar at the top of the Info window closes, open the Terminal app. It's in the Utilities folder of your Applications folder.
  8. Paste or type this command in Terminal, then press Return:

    diskutil resetUserPermissions / `id -u`
    On U.S. keyboards, the ` character is just above the Tab key.

  9. When the process completes, quit Terminal. You should now be able to open Mail and send a message.
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