I would think the easiest way is to use add-on importexporttools to import all your mboxes in to local folders. Then set server settings not to check for new mails or to update every x min

Thank you! Do you know how to set server settings not to check for new mails?

under "Tools" > "Account Settings"

on the left are server settings - select that

uncheck "Check for new messages at startup" uncheck "Automatically check for new messages every __ mins" uncheck "Automatically download new messages"

Thank you very much. :)

I couldn't actually see uncheck "Automatically download new messages"

But actually if there's never anything in the mail account I guess it doesn't matter? It's more a case of ensuring there is no syncing, I don't want all my mail to end up back online. This is an attempt to get rid of all my online mail....

Doesn't seem to be an option not to sync? Unless it's; uncheck; Keep messsages for this account on this computer?

I guess I can just turn the internet off anytime I want to open Thunderbird? To ensure there's no syncing/moving of any more mail....

Either select "Tools" (red arrow) and choose "Account Settings" or right click on your mail box (yellow arrow) and choose "Settings"

a pop up window for the settings will appear

select "Server settings" (green arrow)

then uncheck those boxes in purple

Is that on version 38.2.0?

I only have; check for new messages on startup Check for messages every ** mins When I delete a message Move it to ** folder

yes, those are 38.2 images.

uncheck any boxes that pertain to getting email or logging in, like the first 2 you listed.

Cool thanks.

I'm glad you got an answer. I found all your exchange in Gmail-spam-folder. Cant explain why Gmail suddenly thought Mozillas mail was spam. And it only effected this question.

And in POP3 account you only have those options

Is that on version 38.2.0? I only have; check for new messages on startup Check for messages every ** mins When I delete a message Move it to ** folder

Good luck