TB supports POP, IMAP and SMTP natively, and OWA (Exchange) via add-ons. If the new protocol isn't one of those, it looks like you're out of luck.

Thank you. The consultants were geeking out about security while migrating all of our accounts to MS Outlook 365. So I'll guess OWA is the magic format.

I have had a Google security scan tell me my Thunderbird connection to GMail is a security risk. My AOL account works. Is Thunderbird really that insecure? Is there a plug-in that will help?

TYIA

If the authentication on the gmail account is 'normal password', you have to enable access by 'less-secure apps' in the Google account's security settings, and might be warned of 'risks'. Google may disable acess without prior notice, but if the authentication is OAuth2, access by 'less-secure apps' can be turned off. Similarly with AOL, OAuth2 authentication is recommended.

http://kb.mozillazine.org/Using_Gmail_with_Thunderbird_and_Mozilla_Suite