I&#x27;ve even started seeing registration systems that tell me that I&#x27;ve entered an invalid address if I do the [email]+[something]@gmail.com trick.<p>Twice now I was only able to register after removing the +[something] part of the email.<p>Is + actually an invalid email character (according to RFCs etc?).  I couldn&#x27;t find any reference to that when I looked.