Try the following steps

1. Gmail user name : asdf.mjg@gmail.com
2. Now send mail to as.df.mj.g@gmail.com
3. Now send mail to a.s.d.m.f.j.g@gmail.com
4. Check mail of asdf.mjg@gmail.com

What do you see ? All mails are right inside your Inbox even though you had sent mails to email id which was different. Well actually its different for us but not for Gmail. This is what they say

Gmail allows only one registration for any given username. Once you sign up for a particular username, any dot or capitalization variations are made permanently unavailable for new registration. If you created yourusername@gmail.com, no one can ever register your.username@gmail.com, or Your.user.name@gmail.com. Furthermore, because Gmail doesn’t recognize dots as characters within usernames, adding or removing dots from a Gmail address won’t change the actual destination address. Messages sent to yourusername@gmail.com, your.username@gmail.com, and y.o.u.r.u.s.e.r.n.a.m.e@gmail.com are all delivered to your Inbox, and only yours.

Now if you are thinking that you can sign in to your account without using “.” in your account…try it and you will fail. This is where Gmail checks as its related with security. So now if you are tired of telling people your email id with dots just forget it.