As SMTP protocol specifies, when email message is posted
to Smtp server, client must specify recipient of the
message. For that reason he must issue "RCPT TO:" command. When this happens,
wodSmtpServer will fire MailTo event informing application
about sender. You can specify if you will allow to receive
email messages for such user, or just deny action. For each
"RCPT TO:" you will receive MailTo
event, and application should send message to all users
defined by client.
After event is finished, and during client's
posting, this property will hold email address that client
specified.