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You can download the app and find instructions on how to use it at

Connecting to an individual mailbox

When setting up your account, enter your email address in the format [CRSid] and select 'Configure manually'. Then enter the following server settings:

Incoming server

  • Protocol: IMAP
  • Hostname:
  • Port: 993
  • Connection security: SSL/TLS
  • Authentication method: OAuth2 *
  • Username: [CRSid]

Outgoing server

  • Hostname:
  • Port: 587
  • Connection security: STARTTLS
  • Authentication method: OAuth2 *
  • Username: [CRSid]

When authenticating, you'll see the usual Cambridge University screen for your username, password and then multi-factor authentication (MFA). You must ensure that your username on that screen is [CRSid], and that you use your associated password and additional authentication mechanism.

*If you don't see OAuth2 as an option, fill out the other details and leave the Authentication Method as 'Autodetect'. Click the Re-test button and it should then appear as an option in the drop-down list.

Subscribing to folders

If you have existing subfolders set up in Outlook Online you will need to subscribe to these individually to make them visible in Thunderbird:
1. Select File > Subscribe
2. Check the boxes beside the folders you want to read in Thunderbird
3. Click the Subscribe button
4. Click OK
5. Restart Thunderbird
6. The subscribed folders will be downloaded and will appear separate from the main inbox folder

Deleted Items folder

By default Thunderbird will move deleted items to the Trash folder, this will create a new folder in your Exchange Online mailbox as the default for the mailbox is to use the Deleted Items folder. To ensure deleted items go to the same folder you will need to do the following:
1. Follow the instructions above for subscribing to folders and ensure the 'Deleted Items' folder is ticked. (Restart Thunderbird if you need to tick it)
2. Select Settings> Account Settings
3. Click on Server Settings
4. Under the Server Settings section where it says 'When I delete a message:' click on the drop-down where it says 'Trash on'
5. Select the Deleted Items folder

Connecting to a shared mailbox

Use the following settings to connect to a shared mailbox that you have authority to access. In this example, your username is your individual mailbox in the format [CRSid] and the shared mailbox is in the format [mailbox]@[domain]


  • IMAP server:
  • IMAP port: 993
  • IMAP connection security: SSL/TLS
  • IMAP username: [mailbox]@[domain]
  • IMAP authentication method: OAuth2


  • SMTP server:
  • SMTP port: 587
  • SMTP connection security: STARTTLS
  • SMTP username: [CRSid]
  • SMTP authentication method: OAuth2

When authenticating, you'll see the usual Cambridge University screen for your username, password and then multi-factor authentication (MFA). You must ensure that your username on that screen is [CRSid], not [mailbox]@[domain]


IPv6 connection errors

If you are seeing the error message 'User is authenticated but not connected' please try the following:

  1. Select the Tools menu then Settings option 
  2. Select General, if not already selected, then scroll down and select the 'Config Editor.' button 
  3. In the search box, type ipv4o
  4. Click the pencil icon to the left of "network.dns.ipv4OnlyDomains", type in then select the tick button
  5. Restart Thunderbird.

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