GMail email addresses have a high potential for abuse, primarily in how Google set them up. This is an issue with dots or periods in the username portion of the email address.
Please click here to see Google's explanation on dots or periods in the username portion of a gmail.com email address.
While it is understandable why Google decided to do this, it is definately not standard and is easily exploited by spammers and abusers to create multiple accounts on a site to retain access while their other accounts get banned. In order to stop spam and prevent abuse, we have decided to implement a policy to deactivate any account with a gmail address which contains a dot or period as part of the username portion of the email address, considering that gmail accounts get translated by Google to a username without dots or periods.
Any accounts that are deactivated for this reason will not be reactivated, as a disabled account will prevent further registration attempts with that same dotted email address. The easiest way to avoid this is to not use dots or periods in the username portion of your gmail address.