After initial IMAP synchronization only new messages arriving and sent messages are being synchronized. Are you saying that consumes large amount of bandwidth?

I understand what you are saying, but It happens often enough that I've had cause to reinstall everything and I'd like to just restrict this. we have enough systems and a restrictive internet connection that it would be a good thing to figure out.

Right click the account, select server setting for the account then the advanced button. Set the maximum number of server connections to 1.

I have been using Thunderbird for almost 10 years and have never needed to do a full download from the server of the mail stored there after the initial install of an account. Perhaps you could enlighten me as the the reason someone might need to do this?

I like having everything on my local drive for speedy searches when I'm on the road and have a poor internet connection. Australian Internet sucks basically, I've been to third world countries with better internet than here :)

You do not have to convince me of the Internet here. It is only in the last few years we have had ADSL not 2+ and a reliable mobile coverage. Interestingly the Mobile coverage arrived a year before the internet.

What I am getting at is the need to do a fill download. Even on am IMAP account with a new machine. It is far easier to revert to the old sneaker net and put the files from the old machine on a USB stick and load them on the new machine and then just resume the daily synchronize.

if different computers have different ids for the folder names in the library, can you still do that / sync them?