Deleted Your Thunderbird E-Mail Account by Accident? Here’s the Fix
I just switched web hosts for one of my web sites and created my new e-mail account on Thunderbird. It was late at night, and without thinking, I deleted the old account, along with all of my folders and templates!

This morning I Googled “can i undelete an e-mail account in thunderbird” and found this helpful page:
Recovering deleted mail accounts
Step 1:
Using Tools > Account Settings, create a new e-mail account with the same name as the old one, using the same settings
Step 2:
Locate the folder for the old account in the Thunderbird profile on your computer. Example:
C:\Users\UserName\AppData\Roaming\Thunderbird\Profiles\oadkkice.default\Mail\pop.1and1.com
Note: The “.default” folder on your computer may have a different name. Replace “UserName” with your user name, “oadkkice” with your default folder name, and “pop.1and1.com” with the folder for your old account.
Step 3:
Make sure the old account you just created is selected, then select Tools > Account Settings again. Select Server Settings and locate the Local Directory box. Click the Browse button and select the old account folder you located in Step 2.
Voila! Your old e-mail folders appear. You can now move messages from the old folders into folders in your new account.
Need More Help?
Check the link above for detailed instructions, and if you need additional assistance, visit the Mozilla Thunderbird Support Form
Hope this was helpful!
Have a great day, Christine