Identical responses, different results

[Hobbit User]

Two SMTP servers respond identically if I imitate the bb-services (send
"mail" cr-lf, "quit" cr-lf) dialog using telnet, but give different Hobbit
display results.

[root at bump02 hobbit]# telnet 127.0.0.218 25
Trying 127.0.0.218...
Connected to 127.0.0.218 (127.0.0.218).
Escape character is '^]'.
220 SMTP ESMTP
mail
501 5.5.2 Syntax error in parameters scanning ""
quit
221 2.0.0 p1ie.pen.k12.va.us closing connection
Connection closed by foreign host.

bb-service expects "220", but Hobbit gives a yellow ball and shows banner:

Service smtp on p1ie is not OK : Unexpected service response
554 p1ie.pen.k12.va.us ESMTP not accepting messages
550 5.0.0 Command rejected
221 2.0.0 p1ie.pen.k12.va.us closing connection

However,

[root at bump02 hobbit]#  telnet 127.0.0.206 25
Trying 127.0.0.206...
Connected to 127.0.0.206 (127.0.0.206).
Escape character is '^]'.
220 SMTP ESMTP
mail
501 5.5.2 Syntax error in parameters scanning ""
quit
221 2.0.0 pen3.pen.k12.va.us closing connection
Connection closed by foreign host.

Here Hobbit correctly gives a green ball and shows banner:

Service smtp on pen3.pen.k12.va.us is OK (up)
220 SMTP ESMTP

Any idea why it would give different results for identical client responses?