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Thunderbird IMAP Setup for O365 Outlook in Windows


You can download Mozilla Thunderbird for free from the following Web site:

Click on Thunderbird Free Download icon. Click on Save File button. Please take note where you have saved the file.


  1. Run the downloaded Thunderbird install file.
  2. At the Mozilla Thunderbird Setup window click Next.
  3. Bullet Standard and put a check mark on Use Thunderbird as my default mail application. Click Next.
  4. Click on Install.
  5. Ensure the "Launch Mozilla Thunderbird now" box is checked off and click Finish. Close all Thunderbird windows.


  1. Activate Thunderbird. Click on Cancel to exit all setup screens. You should now be at the Thunderbird main screen.
  2. At the Thunderbird main screen, click on Tools menu and select Account Settings. If you do not see the Tools menu, use the Alt key to bring up the menu bar. From the Account Actions drop down menu, choose Add Mail Account. A window entitled "Mail Account Setup will pop up.
    Screenshot of mail account setup
  3. Type your name, your O365 login ID ( and Passport York password in the provided fields. Optional: place a checkmark in the "Remember Password" box. Click Continue.
  4. Thunderbird will attempt to find the account. Click on the Stop button located at the bottom of the screen.
  5. Screenshot of mail account setup with incoming and outgoing server settings

  6. Setup the screen above as follows:.
    Incoming: IMAP, Server Hostname:, Port: 993, SSL: SSL/TLS, Authentication: Normal Password
    Outgoing: SMTP, Server Hostname:, Port: 587, SSL: STARTTLS, Authentication: Normal Password
    Username:  Incoming:  Outgoing:
  7. Do not modify your personal settings (name, username, password). Click on Re-test button to verify the settings. Click on the Advanced config button.
  8. On the left hand side, under your email address, click on Server Settings. Click on the Advanced… button at the lower right.
    Screenshot of advanced account settings
  9. On the Advanced Account Settings screen verify that there is  check mark beside "Server supports folders that contain sub-folders and messages" and "Use IDLE command if the server supports it". Everything else should be unchecked or blank.
  10. Click on OK twice to exit all setup windows.
  11. Exit Thunderbird. Thunderbird is now configured to access your Mymail account.

Incorporating the York Atlas directory into your Address Book

  1. After starting Mozilla Thunderbird, click on the Tools, Address Book. The Address Book window will appear. Screenshot of address book
  2. Click on the File menu and select New and then LDAP Directory.
  3. Under the General tab, fill in the fields as above:
  4. Name: York Atlas
    Base DN: ou=york atlas, o=york university, c=ca

  5. Click OK to close the Directory Server Properties window.
  6. Click on File and Close to close the Address Book window.
  7. On the Thunderbird window, click Tools and Account Settings...
  8. On the left-hand side, under your email address, select Composition and Addressing.
  9. Under "Addressing" select “Use a different LDAP server” then click on the down-arrow button and select York Atlas.