The last version of Thunderbird to support Windows 7 is 115.18.0 . It can be downloaded here:

https://www.thunderbird.net/en-US/thunderbird/all/

When you eventually are ready to move to Windows 11, I suggest that you install that same version there, then copy your Profile from the Win7 machine to the 11 machine. After you're comfortable that it's working the way you like, THEN upgrade Thunderbird.

But that Thunderbird Version 115.18.0 does not run on Win 11.

so how can i copy that Thunderbird version  to my Win 11 Machine and get it to work ??? ?

But that Thunderbird Version 115.18.0 does not run on Win 11.

It does. I'm running 115.18.0 portable on Win11.

Well, it runs on Windows 10, and I have yet to find anything that runs on 10 that won't run on 11.

And you won't be copying the whole program from the 7 computer to the 11. You'll just be copying your Thunderbird Profile, which is the folder that contains all your personal data (messages, folders, email account info, passwords, etc.)

But now that I think about it some more, I'm not sure there's any real advantage to installing the older version on Windows 11. The Profile from a newer version will probably not be compatible with an older version of the program, but a newer version would probably work fine with an older Profile. I will test that theory tomorrow and report back.

Just to complete the above thought - Thunderbird version 150..0.2 has no problem using a Profile created by version 115.18.0 . But once opened in 150, the Profile probably can't the used in 115 any more because some of its data file formats may have changed.

Has anyone tried what Lin mentioned about version 115 not reading 110 profile correctly  ?

What do you mean by a 110 profile? Lin is giving you great advice, and you're challenging his correctness? He told you that thunderbird has no problem going UP, but can have problem if reverting to older releases.

Hi Better to look at the wording of Lin's kind answer :

. . . . Profile probably can't the used in 115 any more because some of its data file formats may have changed.

i added the quotation marks Bold doesnt work

Keyword is MAY .

Implies that she was  not certain.

So thats why I posted for clarification Im glad people here are helpful. And Lin was kind enough to help and reply.

No reason to attack me. I had a valid reason to post in order to get clarification .

.

Hi Better to look at the wording of Lin's kind answer : . . . . Profile probably can't the used in 115 any more because some of its data file formats may have changed. i added the quotation marks Bold doesnt work Keyword is MAY . Implies that she was not certain. So thats why I posted for clarification Im glad people here are helpful. And Lin was kind enough to help and reply. No reason to attack me. I had a valid reason to post in order to get clarification . .

He/me was/is certain. Ver 150.x can read a 115.x profile - I tried it myself. Data files will be converted to the current formats. 115x will almost certainly have trouble of some kind with a 150x profile. The password database, for one, has changed. I did not try this myself.

Upgrading isn't a problem. Downgrading can be a problem. If you think you may want to downgrade, keep a safety backup copy of your 115 Profile. You should be making regular backups of your Profile anyway.