Gmail doesn’t recognize dots as characters within usernames (email). So when one register with a email like saiful@gmail.com He can register in your wordpress site using same email just by using some of Gmail’s Trick.
- Append a plus
("+")sign and any combination of words or numbers after your email address. For example, if your name wassaiful@gmail.com, you could send mail tosaiful+islam@gmail.comorsaiful+lol@gmail.com. - Insert one or several dots
("+")anywhere in your email address. Gmail doesn’t recognize periods as characters in addresses they just ignore them. For example, you could tell people your address wassaiful@gmail.com,saiful.islam@gmail.comors.a.i.f.u.l@gmail.com.
I decided to solve this issue , so i wrote a plugin which prevent bad guys from using same mail for registration. I wish you guys enjoy this plugin.