An attachment could take you to a login page if your Google account was logged out after you loaded Gmail. I've actually had this happen when I suspended my lap

An attachment could take you to a login page if your Google account was logged out after you loaded Gmail. I've actually had this happen when I suspended my laptop (with a gmail tab open), got on a plane, and opened it again when I got off. When I tried to do something in Gmail again I was logged out (and when I logged in again I got the email from Google "Was this you?")