Strange SMTP problem

(I've submitted a ticket to my ISP's support, but I'm wondering if anyone
here has seen this before.)

Sometime between Monday afternoon and Tuesday morning, my ISP's SMTP
server stopped working.  By that, I mean that this is how the conversation
with the server goes:

  220 mta3.srv.hcvlny.cv.net -- Server ESMTP (Sun Java System Messaging
  Server 6.2-4.03 (built Sep 22 2005))
  helo cv.net
  250 mta3.srv.hcvlny.cv.net OK, MUNGE.optonline.net [69.118.MUNGE].
  mail from: <MUNGE>
  250 2.5.0 Address Ok.
  rcpt to: <MUNGE>
  250 2.1.5 MUNGE OK.
  data


  Connection to host lost.

(The server name in the 220 message varies.)

At first, I thought it was Norton Antivirus, as it would pop up a message
saying something vague about the "connection" being "interrupted".  So I
disabled outgoing e-mail scans, and then Netscape starting complaing that
it got an error from the server, but Netscape claimed that the error was
"2.1.5 MUNGE OK." which didn't make any sense.  (I double-checked, and
code "250" is "success".)  Finally, a direct telnet to the server gave me
the above transcript (more than once), leaving their SMTP server as the
only possible failure point.

-- 
+-------------------------+--------------------+-----------------------------+
| Kenneth J. Brody        | www.hvcomputer.com |                             |
| kenbrody/at\spamcop.net | www.fptech.com     | #include <std_disclaimer.h> |
+-------------------------+--------------------+-----------------------------+
Don't e-mail me at: <mailto:[email protected]>