It depends on what accessory toolbars you're using. On the Google toolbar, there's a little blue wrench ("Adjust...options") at the far right end. Click it and then click "buttons." You'll see a list of toolbar buttons you can select or deselect. Gmail is at the bottom of the list, if you scroll down. Other toolbars must be similar.

I have the same problem. I clicked on the wrench but the only thing that comes up is my e-mail address. When I click that it's asking me to get Google Chrome. I don't want to mess around with it too much, just would like to be able to get my mail instead of always having to type gmail.com all of the time

Any help? Thank you