SMTP
VRFY
#
# Server-side
252 Send some mail and I'll try my best
#
# Client-side
smtp
SMTP external VRFY
smtp://%HOSTIP:%SMTPPORT/%TESTNUMBER --mail-rcpt user@example.net
#
# Verify data after the test has been "shot"
EHLO %TESTNUMBER
VRFY user@example.net
QUIT