Therefore, we decided to list the SMTP commands according to this flow. HELO/EHLO. The HELO command initiates the SMTP session conversation. ... MAIL FROM. The MAIL FROM command initiates a mail transfer. ... RCPT TO. The RCPT TO command specifies the recipient. ... DATA. ... NOOP. ... HELP. ... VRFY and EXPN. ... RSET. More items... Aug 14, 2019