Now this is intriguing. I have seen some gmail user with a @googlemail.com domain rather than the @gmail.com domain in their email address. Doing a quick search, I found the reason why. It seems there is some trademark issue for users in UK and Germany and Google cannot use the gmail if users sign up from those countries.
So if you would like to sign up with a googlemail.com in your email address, it can’t get it done in the normal way. So some bright spark found a way to circumvent it. They noticed the sign up URL has an additional code “&gd=1” . So now all you got to do is click on this sign up link below it will take you to the sign up page with the @ googlemail.com
Do bear in mind if you already have an existing username eg abc123@ gmail.com, you won’t be able to get an abc123@ googlemail.com. Google will automatically reserve that username for either email address.
I tried sending to myself using the @googlemail.com, the message just bounced. But according to one blog, it says you should be able to use both. Anyway, if you want your default to be @ googlemail.com then try signing with the link above.