Gmail and an email client?

I have tried to get Gmail to work with my email client, but it doesnt seem to work. I have tried to use tutorals from Google, and i have tried tutorials from other websites. I have two email clients that i tried to use, one is Opera, and the other one is Tunderbird. Opera and thunderbird seem to work with sending mail, but with Reciving mail, it doesnt work. Thunderbird doesnt show any mail, and Opera shows only one piece of mail that is very very old, one that I have deleted.

So what can i do to fix this problem.

With Opera go to your inbox and in the address bar click the 'rss' button and subscribe for feeds on it.

???
Will that get all the email?

I need to be able to see all the mail. This rss thing, it just gives me a link.
And I need to be able to send mail too.

Doing what I said will only notify you and let you view emails and reply to emails that you have recieved.
Why dont you just do it all from within Gmail?

Why dont you just do it all from within Gmail?

My thoughts as well.

But, then, I don't use an email client.

I use my Gmail account with Thunderbird.. Make sure you have the right addresses entered. You say that you are having problems receiving mail, so make sure the mail server is pop.gmail.com. Also make sure that any usernames or passwords are entered correctly.

My settings are, in the account settings:
Server name: pop.gmail.com
Port: 995 (default)

(ticked) Use secure connection (SSL)
(not ticked) Use secure authentication
(ticked) Check for new messages at start up
(ticked) Check for new messages every 10 minutes
(ticked) Automatically download new messages
(unticked) Fetch headers only
(unticked) Leave messages on server

I hope it helped, if it didn't, I'm sorry.