Thanks katherine. The point is that I don't want them to come after me. I'd like to manage the problem earlier, in a some kind of a "good faith" but I don't have any idea how to do that.
Buy a goldfish. Call it "Goldie". "Goldiemail.com" is already taken (just checked, and it is, indeed taken). So you decided to go with a shortened version since "goldie" was easy to misspell anyway (people might type "goldy" instead and go to the wrong site!

).
For some very strange reason that you can't seem to comprehend, gmail.com is taken, and so is gmail.net and every other TLD. So, you find the wonderful opportunity to get your hands on gmail.(cctld). You now write a blog about Goldie. How he reacts to his new food. How shiny his castle is. And how much of a handsome devil his owner is.
Why "mail" in the domain? You want people to be able to send messages to your goldfish. He's awfully lonely in that fishbowl with no other fish. He could use some correspondence.
Some clowns who say they have rights to the term "gmail" come to you and tell you that that's their trademark.
However, they are sorely mistaken! (and this is not legal advice - merely my perspective - my qualifications consist of reading WIPO cases for fun and about 8 weeks of the 11th grade)
Their trademark is for email services. Your use of the gmail term is for your goldfish. Two different business models.
Perfect example... two businesses, one in job searching, and one in energy drinks, both have the name "Monster". The job searching outfit owns monster.com. Can the energy drink company complain about this? No. Because they're not interfering with one another. You have not interfered with any email business in this case, so what rights can they claim?
Again, this is not legal advice. But it is to the effect of what I would do given such an opportunity.