Micko 2 Junior Poster

Hello,
maybe this is not the right forum, but I hope you'll be able to help.
How many of you used google groups? I have recently signed in but I'm having problem posting new topics. Every time I post it is written my email address (it's partially mask)- I see that other user just use nicknames and if I want to see their email I need to click on "view profile". I'm posting in science groups and these groups are on Usenet. My question is that why my email is used instead of chosen nickname in my profile? I hope there is somebody who had similar problem and can help me.
Thank you very much!