Mozilla Thunderbird and Microsoft Exchange

Recently my domain name registrar, who provides my email, outsourced that service to Microsoft. They asked me to fetch my email either using Microsoft’s web client (Office 365), configure my Outlook client to use Office 365 servers, or configure my 3rd party mail client (i.e., Thunderbird) to use the Office 365 server. Thunderbird doesn’t support MS Exchange out of the box (there is a paid add-on to do so), but it does support IMAP, which is also supported by Office 365.

Configuring Thunderbird to work with Office 365 IMAP was a painless task, and it worked almost automatically — I provided Thunderbird with my email address and password, went through an OAuth permission dialog, and in short order it had automagically determined all the server names and ports to used.

Unfortunately, two problems appeared, and neither Mozilla nor Microsoft seemed to have the right help pages to get past it, and for the first time in forever, even StackOverflow didn’t seem to serve up the right solution.

• In the list folders for the IMAP, only the Inbox folder was displayed
• When sending messages, the error “User is authenticated but not connected” is shown

Thunderbird Doesn’t Display All Folders from an IMAP server.

Setting up Thunderbird to connect to Office 365’s IMAP server went fine, but only my Inbox was populated with any email. None of my folders appeared, even though I coud clearly see them in Outlook’s web interface (https://outlook.office.com).

To solve this, I had to change one of the server settings. Go to the account settings (Edit > Account Settings on Ubuntu or Tools > Account Settings on Windows) and choose Server Settings for the IMAP acount you’ve already set up. Then click Advanced, and finally uncheck Show only subscribed folders.

Restart Thunderbird, let it sync, and your missing folders will finally appear!

User is authenticated but not connected

This error message doesn’t make much sense, at least it’s solveable.

To resolve this error message, you will need to use Thunderbird’s config editor to disable IPv6. I have no idea why this works, but I have verified on three different Windows computers (two desktops, one Surface) that this error message is resolved when disabling IPv6.

1. Open settings (Edit > Settings on Ubuntu, or Tools > Settings on Windows).
2. With the General tab selected at the left, scroll to the very bottom on the right and then click Config Editor.
3. In the search box where it says “Search preference name”, type in disableIPV6
4. One setting will show, with the name network.dns.disableIPv6.
5. At the far right, click the icon with two arrows, to change the value from false to true
6. Close the Advanced Preferences Tab

You should now no longer see that error message, and be able to send and receive messages correctly.

Hope this helps!