see http://kb.mozillazine.org/Recovering_a_missing_profile

I followed the link, accessed the Profile Manager and followed steps. I am unsure what to enter for the "enter a descriptive name for the profile you are recovering." Please advise.

re:System crashed and had to do a clean reinstall If OS Windows, do you see a 'windows.old' folder on desktop ? This may have all your old profile data. So you can simply do a copy paste of your 'windows.old' backup 'Appdata/Thunderbird' folder overwriting the default 'Appdata/Thunderbird' folder and all should be ticketty boo. Do the above with Thunderbird closed.

re : Is there any way to retrieve these emails from the server Note: If you used an imap mail account then all emails are stored on server, so you could just stay with the new default profile name and create a new imap mail account to see emails.

Sometimes, it is possible for Thunderbird to lose where to look for old profile name, hence you can use Profile Manager to create a new one and point it to look at old one, but that assumes the old one is still present.

If the 'Appdata/Thunderbird/Profile/profile name' folder was completely removed because you had to reinstall the OS and then reinstall Thunderbird, then you cannot simply point a new profile to the old as it is not there. After reinstalling thunderbird, a new default profile has already been created, so there is little point creating one with a name created by you.

So check out the 'windows.old' folder local disk C suggestion. If only imap then simply recreate the mail accounts as advised.