Using 587/MSA implies[1] authentication which implies that the client is using a server that is responsible for the email sent through it. [1]: http://en.wikip

Using 587/MSA implies[1] authentication which implies that the client is using a server that is responsible for the email sent through it. [1]: http://en.wikipedia.org/wiki/SMTP_Authentication http://en.wikipedia.org/wiki/SMTP_Authentication