> If an spam email came via SendGrid, Constant Spammer, or MailChump, are you going to be able to tell from the header signatures? Couldn't you always tell thi

> If an spam email came via SendGrid, Constant Spammer, or MailChump, are you going to be able to tell from the header signatures? Couldn't you always tell this from headers? At the very least the recieved headers are going to be a give away.