For those on 3.6*, where changing the version number in the .rdf doesn't apply:
1. Browse yourself to C:\Users\YOUR USER NAME\AppData\Roaming\Mozilla\Firefox\Profiles\A RANDOM CODE IS HERE.default\extensions\
2. Locate the file {582195F5-92E7-40a0-A127-DB71295901D7}.xpi and use WinRaR/WinZip ect. to extract the files
3. Open the components folder, look for the file gmServiceGmail.js and use a text editor to modify the file
4. Look for these 2 lines:
this._loginURL = "https://www.google.com/accounts/ServiceLoginAuth";
should be changed to this
this._loginURL = "https://accounts.google.com/accounts/ServiceLoginAuth?service=mail";
this._loginURL = "https://www.google.com/a/" + this.domain + "/LoginAction2";
should be changed to this
this._loginURL = "https://accounts.google.com/a/"+ar[1]+"/LoginAction2?service=mail";
5. Save the file, overwrite the existing gmServiceGmail.js with this one and VIOLA! After restarting Firefox you should be all set.
I found that I didn't need to unpack anything, I just edited the .js file as directed, saved, and restarted firefox.
Thanks to divrsit for this.
(
https://addons.mozilla.org/en-US/firefo ... r/reviews/)