How do I configure Office 365 email using IMAP?

After reading this article faculty and staff should be able to:

  • Configure an email client using IMAP, for example through Thunderbird
  • Take additional configuration steps to customize Thunderbird
  • Troubleshoot some known issues

Thunderbird is a free email client available from Mozilla.  To install, download it from the Mozilla website and follow their instructions for installing Thunderbird.

IMAP (Internet Message Access Protocol) is an email protocol used for retrieving and storing incoming mail sent over SMTP.


This article applies to Thunderbird.  Thunderbird lacks Exchange support so it needs to be configured for IMAP.  With IMAP you can only access your email, not your calendars, contacts, or tasks.

Setting up Thunderbird

  1.   Launch Thunderbird and choose “Tools” in menu bar and then chose “Account settings”.
  2. Under “Account Actions” chose “Add Mail Account…”
    1. Enter your name as you want it to appear in the From field in outgoing mail.
    2. Enter your IMAP service accounts email address.
    3. Enter your IMAP service accounts password. Then, click Continue.
    4. Thunderbird will attempt to automatically configure your account settings. Click Manual Config.
      • Incoming
        • IMAP
        • Server hostname:
        • Port: 993
        • SSL: SSL/TLS
        • Authentication: Normal Password
      • Outgoing
        • Server Hostname:
        • Port: 857
        • SSL: SSTARTTLS
        • Authentication: Normal Password
      • Username (Incoming): your IMAP service account name
      • UserName (Outgoing):your NetID
      • Click “Advanced Config” Button
      • Click “OK” Button
      •  Click The Thunderbird main window displays.
      • In the left panel, navigate to your Inbox.
      • You may be prompted for your password before your email starts downloading from the server. Enter your IMAP service account password and click OK.


Additional Configuration Steps

We recommend following these additional configuration steps to enable folders which allow you to keep deleted, sent, and drafted items locally on the server.  This allows for these items to be recovered and makes it less confusing if you to access your Office 365 email over any other email clients.


  1. Click on your account name in the left pane.
  2. Right-click and select Subscribe.
  3. Select the Deleted Items folders and then click Subscribe. Repeat this with the Drafts, Sent Items, and any other folders you want to access in Thunderbird.
    • Note: Do not subscribe to the Calendar
  4. Click OK.
  5. Click your account name to display the Thunderbird main window. Under Accounts, click View settings for this account.
  6. In the Accounts Settings window, click Server Settings in the left panel.
  7. In the Server Settings section of the window, under “When I delete a message,” select Move it to this folder and then choose the Deleted Items folder on the server.
  8. Click Copies and Folders in the left panel and make the following changes:
    • When sending messages automatically, place a copy in: select Other and choose the Sent Items folder on the server.
    • Keep message drafts in: select Other and choose your email > Drafts.
  9. Click Junk Settings in the left panel.
  10. Uncheck the box for Enable adaptive junk mail controls for this account.
    • Note: Server side junk/spam filtering is already enabled for Office 365 accounts.
  11. Click OK to save your changes and close the Account Settings window.


Known issues

The following are known issues with Thunderbird:

  1. When sending mail, Thunderbird may hang on the step “Copying Mail to Sent folder.”
  2. You may see an error message that says, “Error copying mail to Sent folder” with a prompt to retry.

To resolve these issues:

  1. In Thunderbird, go to the Tools menu and click Accounts Settings.
  2. In the left panel, click Server Settings.
  3. In the Server Settings section of the window, click the Advanced
  4. Change the Maximum number of server connections to cache to 1 and then click OK.
  5. Click OK to close the Account Settings window.


Keywords: Thunderbird, IMAP, Mac, Windows,

Last Modified: 6/14/17