Follow the instructions in this article: Rebuilding the Global Database

Tried your suggestion Bruce. file shrunk but still in 2013 . sent a mail today to a different URL and it said SENT which I confirmed; also said SAVED and ended properly BUT its not showing in sent folder. On closer look I believe only 2013 files are there no idea where else it could be saving sent messages. thanks but my head is exploding

There is an excellent add-on that can used in this instance. It is called Recover Deleted Messages Add-On, and can be downloaded from that link. Then see Installing an Add-on in Thunderbird.

With it installed, you can right-click a folder in Thunderbird and select "Recover deleted messages", and it will recover any messages that are still in the "mbox" file on the computer, but are not in the index.

If "Compact Folders" has been used, this will not work.

I have tried all above with no luck. gave up and following another suggested path which would lose my messages. I saved sent file and sent.msf then deleted both from profile while Thunderbird was closed I was told and expected the sent file to be rebuilt with no messages in it. I never got rebuilt even after sending messages.. How do I get a new sent file?

Perhaps the Sent index file was out of synch with the actual 'Sent' file containing the emails.

Close thunderbird. Put the 'Sent' (no extension) file back into the mail account from where you removed it.

Start Thunderbird and a new 'Sent.msf' file will be auto generated. This rebuilds the index showing what is in the 'Sent' file.

Report back on results.

Is this a pop mail account you are talking about?