I think you will need to provide a bit more description of what you are changing from and what exactly you want to change... and maybe why this change is needed. Do you really mean just changing the server address but keeping the same account with the same email provider? If you are using IMAP then what emails you see depends on whether the provider of your email service has all your email on that new server address.

What I'm asking is what I need to do in order to protect my emails if I change server information or change service provider. This question stems from the fact that I have all my emails set up as IMAP so that people can access them on various computers (they can switch from laptop to desktop no matter where they are). Since they often work from home and are in constant receipt of documents - I need to know what would happen to those emails if we changed providers. Current one had a massive meltdown of their servers and we had to rebuild everything. Despite people having all their emails (until the meltdown) ON their computers (fully accessible and able to read, copy, etc while offline) the second I changed the server information on their account to the new email server I was given, it caused all the emails to disappear. (They were still on the system so I was able to restore it).

I want to know if I change providers, and by association change all the server info, will Ihave to deal with this again or is there something I can do so that the emails just transition over.

Well yes, if you change providers you need to save every email you want to keep from IMAP to your local machine, or, transfer them from one provider to the other if that is possible. As it seems you are IT for a corporate email system, I can't really help further - my experience is as an end user. Someone may know a way to save them all in a local networked server and provide access to that maybe via VPN, but that's beyond the scope of Thunderbird forum. End users saving them locally - use Local Folders location, set up a folder structure if you wish, and copy the emails into Local Folders. Then back up each profile to preserve both the emails and your settings. Offline folders as you found out are still subject to syncing with the IMAP mail server; Local Folders are truly local - but on each computer, not accessible from multiple devices.

Not IT unfortunately. Just a worker bee that has no patience for tech support. :D Thanks.