Special symbols in email/username

Hi Telerik Team and everyone!

I have an issue with standard Login widget.
Our team have implemented registration logic. Username/email can be like this - aaa+aaa@bb.b.ccc or sss-kkk@lll-fff.ppp and user can be successfully registered with such emails.
But we use standand login widget that generates error message when you're trying to login with email special characters like "+". Login with characters "." and "-" work fine.

Help me to resolve this problem, please.