EHLO with an Old Mailer
$ telnet/port=25 arizvm1.ccit.arizona.edu.
Trying... Connected to ARIZVM1.CCIT.ARIZONA.EDU, an IBM 3090-300E running VM/XA.
220 ARIZVM1.ccit.arizona.edu running IBM VM SMTP V2R2 on Tue, 25 Apr 95 21:09:1T
500 Unknown command, 'ehlo'