First the user's name is verified, then an attempt is made to send to the user's terminal. When that fails, the messages is mailed to the user's mailbox.
R: 220 SU-SCORE.ARPA Simple Mail Transfer Service Ready
S: HELO MIT-MC.ARPA
R: 250 SU-SCORE.ARPA
S: VRFY Crispin
R: 250 Mark Crispin <Admin.MRC@SU-SCORE.ARPA>
S: SEND FROM:<EAK@MIT-MC.ARPA>
R: 250 OK
S: RCPT TO:<Admin.MRC@SU-SCORE.ARPA>
R: 450 User not active now
S: RSET
R: 250 OK
S: MAIL FROM:<EAK@MIT-MC.ARPA>
R: 250 OK
S: RCPT TO:<Admin.MRC@SU-SCORE.ARPA>
R: 250 OK
S: DATA
R: 354 Start mail input; end with <CRLF>.<CRLF>
S: Blah blah blah...
S: ...etc. etc. etc.
S: .
R: 250 OK
S: QUIT
R: 221 SU-SCORE.ARPA Service closing transmission channel
Scenario 5
Doing the preceding scenario more efficiently.
R: 220 SU-SCORE.ARPA Simple Mail Transfer Service Ready
S: HELO MIT-MC.ARPA
R: 250 SU-SCORE.ARPA
S: VRFY Crispin
R: 250 Mark Crispin <Admin.MRC@SU-SCORE.ARPA>
S: SOML FROM:<EAK@MIT-MC.ARPA>
R: 250 OK
S: RCPT TO:<Admin.MRC@SU-SCORE.ARPA>
R: 250 User not active now, so will do mail.
S: DATA
R: 354 Start mail input; end with <CRLF>.<CRLF>
S: Blah blah blah...
S: ...etc. etc. etc.
S: .
R: 250 OK
S: QUIT
R: 221 SU-SCORE.ARPA Service closing transmission channel
Scenario 6