Sub-addressing with '+' is a common (but not universal) email hosting feature that predates Gmail. What's more particular to Gmail is zero or more periods '.' b

Sub-addressing with '+' is a common (but not universal) email hosting feature that predates Gmail. What's more particular to Gmail is zero or more periods '.' being ignored so awinter-py, a.winter-py, and a.wint.er.py are all equivalent and valid on Gmail.