Hi Loredana, all, I deal with mails in full text-mode for years. I don't use GMail so I can't say anything on that, but for the rest I am a happy mutt user. I use emacs just to compose the messages, but to deal with them, including reading them through IMAP or POP I use mutt. The only disadvantage I see to this is that I have no filters but I had in the past. At that time I used fetchmail to read the e-mails from the server and then let them go through procmail, the old way. There are probably better alternatives to fetchmail todays, it has a bad reputation. Regarding reading and indexig e-mails mutt is no longer the state of the art either, I think. You may have a look to the notmuch and alot tools.
Hope this helps, Shérab.