I’ve received a couple e-mails concerning the link in the Get Mail Extension entry not working. After a little research I found out the extension was no longer on the main AMO (addons.mozilla.org) section or even in the sandbox. Further research via Google I found out the author’s site for Get Mail (he also did ChromEdit Plus) extensions.  From the Get Mail FAQs:

When AMO recently updated their site… It was MY personal decision to remove ALL of my extensions from AMO at this point in time.

All of his extensions are hosted on his webdesigns site. The link in the Get Mail Extension entry has been updated.