Trying to understand how TB Portable syncs before and after travel. How large flash drive do I need for TBP? When I get back after trip, does TBP back up TB with the changes I made while traveling? Would it be possible to leave flash drive in PC and run TBP all the time and then take the drive on trip? Thanks.
Your absolute best option is to use IMAP and keep your email and primary folders on the server. You can then access all your mail from your desktop, laptop, tablet, phone, and Thunderbird Portable. You can use your desktop (or whatever has connection to a backup drive) to pull stuff offline when space is an issue or you wish local copies of critical data.
Sometimes, the impossible can become possible, if you're awesome!