Do all email providers ignore periods in front of @?

I know that gmail lets a user insert as many periods as he/she wants in an email address before the @ sign. Gmail also lets users append the email address like this: userName+anyStringHere@gmail.com. All those "different" email addresses are essentially the same address. (Link to google blog describing these "features")

I want to prevent users from creating multiple accounts with what is essentially the same email address. I decided to store email addresses in my database with those periods and anything following and including a + sing stripped, but now I am wondering: Is it a standard to ignore periods in front of the @ sign that email providers are mostly following?