Compatibility with Gmail's newer authentication method (OAuth2) was added in Thunderbird 38.0.1, released in July 2015.

The current release of Thunderbird supports Windows Vista: https://www.mozilla.org/thunderbird/38.4.0/system-requirements/

I'm not sure of the best way to update... You might want to back up your mail stores first. For example, you could make a copy of your Thunderbird profile folder. See: Profiles - Where Thunderbird stores your messages and other user data.

And then... I'd wait for additional suggestions.

Only after I changed the setting in Gmail to allow low security apps would Gmail allow me back into my mail via Thunderbird.

This is a requirement imposed by Google, not Thunderbird. If the 'allow less secure apps' setting gives you an unpleasant feeling you may consider 2-step authentication in connection with application specific passwords. https://support.google.com/accounts/topic/28786?hl=en&ref_topic=3382253

Having said that, updating to the latest version would be recommended regardless. The best way for updating is using the built-in update mechanism. This ensures that also your profile gets updated properly in case there were significant changes between major versions.

I have auto update set in Thunderbird but it will not go past ver 15.

Have you tried to manually checking for updates? At the top right of the Thunderbird window, click the menu button , then select Help > About Thunderbird.

In case that fails, I'd download the full installer for TB v17.0.9 and run it. Then try the incremental update again, until you're at the latest version (38.4.0). You can get v17 at https://ftp.mozilla.org/pub/thunderbird/releases/17.0.9esr/win32/

Use the link for your desired language.

Once updated to v38, you'll need to set 'Authentication method' to 'OAuth2' in your account settings for both, incoming and outgoing server. This then obsoletes the 'allow less secure apps' setting.

christ1: Thanks for the info....all good stuff. I was able to update to 17.0.9 using your instructions. But, when I go thru the manual update process under 17.0.9, it just tells me I am up to date. Can I download and install v38.4.0 directly from the web without messing up my entire mail filing system?

Thanks again, Richard

You probably can. But to be on the safe side, I'd do one more intermediate step downloading TB v31.8.0. https://ftp.mozilla.org/pub/thunderbird/releases/31.8.0/win32/

If incremental updates still don't work then get the latest version from https://www.mozilla.org/en-US/thunderbird/

You might want to back up your mail stores first.

That's certainly something you should have done by now. http://kb.mozillazine.org/Thunderbird_:_FAQs_:_Backing_Up_and_Restoring

christ1: OK. I backed up my profile using MozBackup. Then down loaded and installed v31.8.0. Tested functionality of T'bird and all OK. Then ran a manual search for updates (via menu in upper right corner of window). Once the update(s) were installed, "About T'bird" showed I was running v38.4.0. I then tried to set server Authentication Method to "OAuth2" but that option was not avail. in the drop down box. The only options were: Normal Password, Encrypted Password, Kerberos/GSSAPI, NTLM, and TLS Certificate. I left it at the default of Normal Password. I went to Gmail and set "allow less secure apps" to "No". When I tried to sign on to Gmail via T'bird, it would not allow. I set the "allow less secure apps" to "Yes" and I could sign on the Gmail via T'bird. While I am a little uncomfortable with that setting, I guess I will leave it that way. At least I am up-to-date on Thunderbird and can keep up with future updates.

Thanks so much for all of your help.

Richard

I then tried to set server Authentication Method to "OAuth2" but that option was not avail. in the drop down box.

'OAuth2' only works for IMAP accounts. For POP 'Normal Password' is required, either in connection with 'allow less secure apps' or 2-step authentication.

You can set 'OAuth2' for the Outgoing server/SMTP though.

When your problem has been fixed can you mark the thread as 'Solved' please? Thank you.

christ1: I found the place to set the Outgoing server to "OAuth2" and did so.

Thanks again for all of your help.

I will mark the thread as solved.

Richard