Cannot send email with Thunderbird client

Question

I have been able to setup my office365 business email account using Thunderbird 43.0.1 (aarch64) - which is the latest version available. For whatever reason I cannot send email, but I can receive email, sync all of my folders, even store drafts that synchronize with the server, but no emails messages will send. What a fun problem this is...

I am pretty surprised that all of the other syncing is working but not send. I guess this is where the

Any explanation of how this could be done correctly would be great!

Answer 1

Hello @Ryan Mohrman

Thanks for sharing the screenshots and details.

From what I can see, your account is currently set up in Thunderbird using IMAP. However, if your email account is part of your organization’s Microsoft 365 environment, it’s likely an Exchange-type account.

To confirm this, you can open Outlook, go to the File > Info section, and check the account type listed there.

If it says Exchange, I recommend setting up your account in Thunderbird using the Exchange option instead of IMAP.

You can follow this official guide from Mozilla: Thunderbird and Exchange – Mozilla Support

(Note: Microsoft is providing this information as a convenience to you. The sites are not controlled by Microsoft. Microsoft cannot make any representations regarding the quality, safety, or suitability of any software or information found there. Please make sure that you completely understand the risk before retrieving any suggestions from the above link)

I’ve tested this setup in my own environment, and when using the Exchange option, Thunderbird automatically configures the account for you, no manual setup is needed. I was able to send and receive emails normally.

If you’ve tried this and the issue still persists, I suggest contacting your IT administrator to check whether there are any restrictions applied to your account that might be blocking Thunderbird.

If your IT confirms that everything looks fine on their end, I recommend asking them to open a support ticket with Microsoft so the backend can be reviewed in more detail.

I hope this helps! Let me know how it goes or if you need further assistance.

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