Rename the current prefs.js to prefs.js.bak, then copy the prefs.js from the backup into the profile folder, restart TB, and see if the missing account appears. Note that Identities are defined within an account, and don't appear in the Folder Pane or Account Settings in the left pane.

Thanks for the suggestion. Unfortunately it did not work. I found out that the two lines posted above are removed from prefs.js as soon as I open Thunderbird, i.e., even before I type in the password for my profile. I wonder if:

- Thunderbird reads the prefs from somwhere else, or - Thunderbirds finds something wrong and changes the prefs.

I also noted, that all the information for my account still seems to be in prefs.js. I have lots of entries for

- mail.identity.id4.*, and - mail.server.server7.*

I am not using Identities. I am using a profile with multiple E-Mail accounts from different providers.

Any Ideas?

I have come across another case regarding preferences that were not being kept - not accounts, but a paragraph default setting when composing, but same issue in that upon restart the 'prefs.js' file was appearing to get overwritten and losing preferences.

They had a second 'profile name' folder listed. It had a preference set to a default setting which - For some unknown reason - was forcing a completely different profile to be unable to change that default setting. Once they had accessed that other profile and manually altered the 'prefs.js' file and also manually altered the same in the profile they did use. All worked. Sounds weird but true.

In the Appdata/Roaming/Thunderbird/'Profiles' folder - do you have more than one 'profile name' folder ? Is there perhaps an old profile which you stopped using due to issues? Do you use more than one profile ?

Thanks for pointing that out. I do have more than one Profiles folder but use only one. I think there are more than one due to trying out different things. Is it safe to delete the unused folders?

You can remove any profile you do not use assuming there is nothing of any value in that profile. Make sure you do know which profile is the one to remove as it is not the sort of thing you would want to get wrong. So double check.

It is best to remove it via the Profile Manager: Exit Thunderbird Start Profile Manager select profile you want to remove click on 'Delete Profile' select 'Delete files' to completely remove Then click on Exit as you do not want to start Thunderbird just yet.

Good info here:

• https://support.mozilla.org/en-US/kb/profile-manager-create-and-remove-thunderbird-profiles#w_start-the-profile-manager-when-thunderbird-is-closed

Access the good profile name folder and repeat instructions offered by sfhowes regarding using/replacing prefs.js from the backup. Then delete these files:

• folderTree.json
• panacea.dat
• session.json

Check to see if the actual account still exists as you may need to copy that mail account name folder from backup as well. I'm assuming this is a pop account click on 'Mail' folder it will list all pop acounts - is the account still there - hopefully yes as pop account folders do not usually get removed unless manually deleted.

Then Start Thunderbird and see if it picks it up.

If still a problem... Please note: If POP account, you could create a new existing mail account for email address and then in Account Settings > Server Settings change the 'Local Directory: to point to the original pop mail account folders that are still lurking in the profile 'Mail' folder and then restart Thunderbird.

Hm, did all that but the account still did not show up. So I went with re-creating it as suggested, which worked. Didn't set the local directoy though as it was an exchange account and I now decided to use it via IMAP. At least I cleaned up my profiles, renamed the one I use, and learned about Thunderbird :)

Thanks for all the help!