Hi:
Ah, OK, thanks for the clarification.
I guess your ISP provides a "branded" version of Yahoo webmail.
And thanks for confirming that IE works OK.
That narrows it down to a Firefox problem.
It's really not a problem with "opening links in emails", as first described. That's what had me confused.
The problem seems instead to be that a link to an email address on a web page in Firefox is not opening a new email in your Yahoo mail.
1) One entirely reversible step would be to try "Mozilla Safe Mode".
(NOTE: this is NOT the same thing as "Windows Safe Mode").
It's just a way to temporarily and generically debug Firefox by starting it with certain add-ons and extensions disabled. Be sure
NOT to check anything that sounds like "Reset Firefox" or "Permanent Changes" -- you only want to do this reversibly for testing. And it might be good idea to
back up your profile first, and/or to print out and read the instructions carefully before proceeding.
See here:
Safe Mode
or here:
Troubleshoot Firefox issues using Safe Mode
2) Another step to try would be
TEMPORARILY pause real-time protection of your VIPRE AV/Firewall and test again. If that resolves the issue, then it might be some setting in your AV or firewall.
Be sure to enable your VIPRE AV/firewall immediately after you try this.
3) There may be other, more specific help here:
Fix problems with websites (Facebook, YouTube, webmail etc.)
Hope this helps,