My Bad! I didn't bump any version numbers because of no new features.
I DID bump the max version to Firefox 3.5 in all of the install.rdf's. Sooo...
For Firefox 3.5... Just reinstall these versions over the old and they will work!

Adds easy access to your computers default email program.
"Visual Refresh" 24px & 16px icons and a "Tools" menu entry.
Uses the Windows keyboard shortcut for "New Message" - CTRL + M
*NOTICE - The keyboard shortcut works in Windows & Linux ONLY!
Shortcut to "Read Mail" - Just double click on the toolbar icon!
Get Mail Version 2.5.4
Install | Save To Desktop | [Screenshot]

Works In...  2.0.0.*    0.8 - 1.0

Operating Systems...

Get Mail Plus Version 3.0
This version's goal is to deal with the Windows problem of incorrect access to the
Default email program when you click on "Read Mail". By default, the path is set
to access a normal Thunderbird install on Windows. This can be easily changed
through the Options window. "New Message" is not affected by these settings.
For use with other email programs, just enter the path in the Options window.
Example:  C:\Program Files\Outlook Express\MSIMN.EXE  - Usual path to O.E.
NOTICE! When pasting paths into the Options window, DO NOT include the " "
Get Mail Plus Version 3.0
Install | Save To Desktop | [Screenshot]

Works In...  2.0.0.*    0.8 - 1.0

Get Mail Frequently Asked Questions:

Q: I've installed the Get Mail extension, but there is no Mail icon on my toolbar.
A: Right-click on any part of the toolbar that is not a text box (or View > Toolbars)
and select Customize... This will bring up the Customize Toolbar box. Drag the Get Mail
icon from the box to where you want it on a toolbar... then click on the "Done" button.

Q: Can I set Get Mail to access my Hot Mail, Gmail or Yahoo mail directly?
A: NO! Get Mail is designed to access your DEFAULT EMAIL PROGRAM ONLY!
Thunderbird, Outlook Express, etc.. are stand alone email programs. Hot Mail, Gmail
and Yahoo are Webmail apps that can be setup for use with an actual email program.

Q: Nothing happens when I click on "New Message" How can I fix this?
A: Type about:config in the urlbar... click "Go" or hit enter.
Scroll down and find   network.protocol-handler.external.mailto
Make sure it's value is set to true.

If your having problems setting and accessing the default email program...
Most problems seem to be with Windows. Please try the steps below one at a time.

Step 1. Do the obvious! Make sure the email program you are trying to access is set as
default through the program itself.

Step 2. Go to Start > Set Program Access and Defaults > click Custom.
Set the default email program of choice there.
You may need to restart your computer for this change to take affect.

Step 3. Use The Windows Default Mail Utility. Or...
Use Get Mail Plus listed above.

Step 4. If NONE of MY known solutions posted above solve your problem...
Please use the MozillaZine Firefox Support forum where you may find more possible solutions have been posted.