Troubleshoot Errors in macOS Sierra Mail Setup

User Name :
Your user name is your full email address
Incoming Server :
Ports : IMAP 143 / POP 110
Outgoing Server :
Port : SMTP 587


This guide will help you fix errors in the setup of macOS Sierra Mail.


  • Is this the first time you’re setting up this email account? Then use our macOS Sierra setup guide, rather than this troubleshooting guide.
  • Change to your domain name

Check account settings

  1. From the top menu choose Mail > Preferences…


    Account Information

  2. On the Accounts tab, choose the relevant account from the list on the left, and check:
    • Enable this account is checked
    • Download attachments is set according to your preference
  3. Click Server Settings


    Server Settings

  4. Check:


  5. Deselect (uncheck) the boxes for Automatically manage connection settings for both Incoming and Outgoing Mail Servers – additional fields will now be displayed.
  6. Select Advanced IMAP Settingssierra-advanced-imap
  7. Select Allow insecure authentication > OK


  8. Deselect (uncheck) the boxes for Use TSL/SSL for both Incoming and Outgoing Mail
  9. Click Save. (Note: this button only becomes visible when settings have changed)

    Your macOS Sierra mail is now setup correctly.

Still struggling? Refer to our guide of common email problems or contact