Search results for " 551 Command RCPT"

SMTP basics - What is SMTP?

Overview The SMTP protocol is a simple text based set of rules that establish how two mail servers communicates between. It is a 2 way communication as stated in RFC 821 : "as the result of a user mail request, the sender-SMTP establishes a two-way transmission channel to a receiver-SMTP. The receiver-SMTP may be either the ultimate destination or ...