The closest alternative you can do to this, is set-up pop3 e-mail checking in Messenger Plus! (by going to preferences > POP3 E-Mail) then click on More Options... and type in
http://www.gmail.com into the box.
This wont work in the exact same way, but to quickly go to your e-mail you can click on the Plus! icon in the contact list and then click on "E-Mails in yourname@gmail.com: X"