I have two computers, each has Thunderbird installed.
I once set up a Thunderbird profile on computer A and configured my email accounts there (all POP3, not IMAP). The message store type is "File per folder (MBox)".
Later I copied that profile to computer B and used them in parallel.
So now both profiles still have the same name and some common data and settings, but e.g. the sent mails are only located on the computer they were written. Received mails are mostly on both computers, because the mail server keeps read messages for another month or so, which means I usually have time to download them from both machines.
My question is how to bidirectionally synchronize those two profiles again, so that at least all the data (sent/received mails) is the same on both computers? I don't want to upload the profile folders or mail files anywhere, so please suggest methods that work locally (I could of course transfer the profile folders per pendrive etc.) or over LAN.
Please note that I don't really want to migrate all my stuff to IMAP (although it would be supported) - I just want to be able to synchronize the POP3 Thunderbird clients manually, on demand over my local network or using removable storage devices.
The question is not about migrating to IMAP to keep the accounts in sync in the future, my main problem is to synchronize the past: mails that got already deleted from the server and are stored only in one local profile, and sent mails which were never stored on the server and are only located in the profile from which I wrote them.