[aorth]

The Thunderbird blog post also mentions they are looking to support the Microsoft Graph.

More limiting is that the current release doesn't support custom Office365 tenant IDs. So basically, unless you are using outlook.com this won't currently work yet. I'm lucky that my org hasn't disabled SMTP and IMAP, but it's been so slow lately...

[bangaladore]

Someone might be wondering why someone might have different URLs. One example is anyone under sovereign clouds (eg. GCC, GCC-High) which use different URLs (and TLDs) across the board (eg outlook.office365.us)