Julie, My suggestion: - click file>offline>download to ensure all online messages are downloaded - then do your own check to be sure you see them there. - highlight the folder and use the Importexport addon to 'export remote folder' - now click 'local folders' rightclick and create new folder - highlight folder and start inportexport utility and select 'import messages' - in saved folder, click until you see the messages and click OK - when one, compare the messages in Offic365 inbox with those in local folder. Once you're okay you can remove the account, as you now have all messages saved locally.

AND, I'm sure there are other ways to do this, but that's how I would do it.

If you have a pop mail account then emails are stored on your computer. There is no synchronising between the pop folders and the server folders. They will remain in account.

But, I'm assuming you have an imap mail account in which case emails are stored on the server and you get to see emails because the imap folders synchronise with server folders so they can display what is on the server. Do not assume the imap folders are independent. You do not want any imap folder synchronising with an empty server. I would advise you get copies of fully downloaded emails into your Local Folders mail account before you remove any account.

I would advise that you make sure you have set up all your folders and subfolders to download full copies and not just headers.

• Account Settings > Synchronisation & Storage for the mail account
• Select : 'Keep mesages in all folders for this account on this computer'
• Click on 'Advanced..' button
• Check all the folders and subfolders have their checkboxes selected.
• click on 'OK'

• Select 'Synchronise all messages locally regardless of age'

Then make sure all folders are up to date by doing this:

• Menu icon > File > Offline > Download/Sync now
• Select 'Mail Mesasges'
• Select 'Work offline once download and/or synchronisation is complete.'
• The 'Select' button offers you the chance to check all the folders are selected.

• Click on 'OK' to start process.

Wait until all is complete and Thunderbird has gone into 'Offline' mode as indicated by the icon on bottom left in Status bar. To get copies of emails, it is much easier to do this without constantly synchronising with server - hence Offline mode.

Whilst in Offline mode, I advise you do the following.

• Create suitably named folders inthe 'Local Folders' mail account.
• Select an imap folder eg: Inbox
• Select a batch of emails to highlight.
• Right click on highlighted emails and use 'Copy to' and select the relevant folder in the 'Local Folders' mail account.
• Repeat this process until you have got a complete copy of everything in the 'Local Folders' mail account.

In Local Folders account, Check you can read various random emails in various folders to check you have got good copies. The folders in the 'Local Folders' mail account do not synchronise with server. These emails are stored on your computer. There is no synchronisation with server folders.

At this point you can go back into 'Online' mode. Click on the 'offline/online' icon in bottom left of Status bar.

Now you have the opportunity to delete all your emails that are in the imap account. Then compact the imap folders. This will make sure all your emails get deleted off the server. Then you can remove the imap account in Thunderbird and finally remove the account from Office365.

All old Office365 emails will now be fully accessible via Local Folders mail account.

I will give this a try. Thank you so much for the detailed explanations. I am immensely grateful for your responses!

You're very welcome. If you encounter problems, please share.

I was able to get the emails and sub-folders all transferred to a local folder for backup purposes. SUCCESS!

I was able to get the inbox emails combined into the new pop3 account that is hosted at SiteGround. SUCCESS!

I have the synchronization selected so that the pop3 account will keep a copy of the emails on their server. So now I'm waiting for that to sync. I think I've checked all the boxes in all of the right spots on both SiteGround and in Thunderbird. But if anyone has any specific tips on that last step to get everything uploaded from the Thunderbird pop3 inbox (at Siteground) to the Siteground webmail application...that's my last step, I think.

I may just need to patiently wait for that.

Again, THANK YOU for the support here today. I'm so grateful!