Nope, there is no restriction for plus addresses. I validate email addresses and specifically allow + and . in the part before the @ sign. myemail+1@mydomain.co

Nope, there is no restriction for plus addresses. I validate email addresses and specifically allow + and . in the part before the @ sign. myemail+1@mydomain.com and myemail+2@mydomain.com will be considered two different users. Have to add also that the "plus feature" isn't a Gmail-specific invention but a standardized way of referring to the same mailbox using different addresses. But some email providers don't support this feature, and many input validators out on the Internet don't either.