Do you still have these prefs on the about:config page?

gecko.handlerService.schemes.mailto.1.name  value: Gmail
gecko.handlerService.schemes.mailto.1.uriTemplate value: https://mail.google.com/mail/?extsrc=mailto&url=%s

You can open about: pages via the location bar like you open a website.

Yes, i still have them, just checked...

Try to delete mimeTypes.rdf in the Firefox Profile Folder

• http://kb.mozillazine.org/mimeTypes.rdf
• http://kb.mozillazine.org/File_types_and_download_actions#Resetting_download_actions

Tried to rename it, didn't work, firefox didn't even create another mimeTypes.rdf after restarting it...

Did you remove the file in the correct Firefox Profile Folder

• Help > Troubleshooting Information > Profile Directory: Open Containing Folder

• http://kb.mozillazine.org/Profile_folder_-_Firefox

yes, i deleted in the wrong dir.

everything is back now to normal, thank you very much for the help :)

zenzo, how did you fix the original problem - I have the same problem - nothing happens when clicking on mailto links.

Please detail every step to take, also to avoid the problem you list here.

First make sure that you have set a default mail program.

• https://support.mozilla.com/kb/Changing+the+e-mail+program+used+by+Firefox

Did you check the Mailto setting in Firefox/Tools > Options > Applications ?

• Press F10 or tap the Alt key to bring up the "Menu Bar" temporarily if the Menu Bar is hidden.
• Use "Firefox > Options" instead of "Tools > Options" if the menu bar is hidden.

If that doesn't include your e-mail program then go to the Firefox Profile Folder and delete the file mimeTypes.rdf to reset all download actions.

• http://kb.mozillazine.org/Profile_folder_-_Firefox
• Help > Troubleshooting Information > Profile Directory: Open Containing Folder