The limitation cited in the previous post
does period(.) make a difference?
is not the google's limitation. Rather, it's a feature of Google. Read below.
The content below is taken from wikepedia...............................
Local-part normalization
Interpretation of the local-part of an email address is dependent on the conventions and policies implemented in the mail server. For example, case-sensitivity may distinguish mailboxes differing only in capitalization of characters of the local-part, although this is not very common.[3] GMail (GoogleMail) ignores all dots in the local-part for the purposes of determining account identity.[4] This prevents the creation of user accounts
your.user.name or yourusername when the account your.username already exists.