Hello Amir,
Welcome to the group.
I see that you are using Selenium IDE.
My first suggestion is to migrate to Selenium 2 so that you can take full advantages of a real programming language.
Now for Gmail I would not suggest using Gmail UI for such operations. Gmail is filled with frames and Google changes its UI very often. I would rather suggest to use java mail API to exercise Gmail. You might get idea using this post -
http://www.seleniumtests.com/2011/08/verify-email-confirmation-using.html?utm_source=BP_recent
~ seleniumtests.com