Clicking on Mail to links opens Gmail instead of Eudora

I love Firefox - I've had it installed for a year or more but suddenly
it has changed to start acting like a Microsoft product. In the past,
when I clicked on mail to links, my defualt mail application was opened
- Eudora. Suddenly, I click on a mail to link and Gmail opens. I didn't
install any new software, extensions, preferences or anything. It
suddenly started behaving in this odd way.

My troubleshooting so far includes:
I went the route of Tools-Folder Options-File Types but there's nothing
in there for Mail to.
I loaded the same page in IE and clicked on the same link and Eudora
opened so my change is not global, just in Firefox.
In Firefox Options-Downloads-View and Edit Files, there is no reference
to Mail to command.

Any help would be appreciated. If this is not the correct forum,
apologies and please direct me to a better place to post this.

Thanks
Dave

sfplayers@gmail.com