Do you have synchronization enabled? (Select an account, go to: Tools -> Account Settings. Then select synchronization & storage in the left pane. Check whether if "Keep messages for this account is enabled". You can also select which folders are stored in this way if you select "Advanced...")

Thank you. Yes, 'Keep messages...' is enabled.

What worries me still is if I go to Gmail and delete a message there it is immediately deleted from TB which is exactly what I am aiming to avoid. Is there something else I should be checking also?

You are correct. The above advice helps you have copies of mail when offline. If he server gets deleted the next time Thunderbird's syncs with zero messages on the server you wind up with zero. To get messages on your local drive and out of control of providers server you make folders under the Local Folders account and move them there. The other option is to use POP instead of IMAP. You should Google the differences between the 2 protocols and decide what works best for you.

Ah, thank you. Now I understand the function of 'local folders', that makes sense. Is there a way to have all messages, incoming and outgoing automatically move to local folders?

Also, with synchronization enabled a backup usually helps if something bad happens. https://support.mozilla.org/kb/profiles-where-thunderbird-stores-user-data#w_backing-up-a-profile

christ1 said

Also, with synchronization enabled a backup usually helps if something bad happens. https://support.mozilla.org/kb/profiles-where-thunderbird-stores-user-data#w_backing-up-a-profile

Thanks, I need a belt and braces solution after a near disastrous loss of data solved only by quick action and great service from Google/Gmail and mail.com. Local folders and a backup will make me feel safer!

Is there a way to have all messages, incoming and outgoing automatically move to local folders?

Having set up folders to keep copies in my mail account. My personal preference is to synchronise folders for offline use. Then in 'Offline' mode to stop further synchronising whilst I'm making working on those imap folders, I makes copies of emails I want to keep and put them in a suitable folder in Local Folders.

Also in 'Offline ' mode you can check a proper copy was downloaded. If you can read the email, then it was downloaded correctly. I use this when I need to copy a batch of emails.

'Menu icon' > 'File' > 'Offline' > 'download/synch Now'

You can also set up a Message Filter to auto put copies in Local Folders. It is worth double checking that they did get correctly copied. 'Menu icon' > 'Message filter' > 'Message Filters' select correct imap mail account. click on 'New'. Create filter. Make sure filter is enabled.

Good info on message filters:

• https://support.mozilla.org/en-US/kb/organize-your-messages-using-filters

I would also advise that you backup your Profile name folder to an external harddrive on a regualr basis, eg: monthly. Depends upon how many emails you get and personal preference.

Profile location:

• http://kb.mozillazine.org/Profile_folder_-_Thunderbird