The complete error message was "Task 'MSN - Receiving' reported error
(0x800CCC0F): 'The connection to the server was interrupted.  If this
problem continues, contact your server administrator or Internet
service provider (ISP).'"

This is a legacy pop3 account, maintained as noted through a fee-based
MSN Premium account.  I have SPA checked because Microsoft states that
SPA is required, and the OL 2003 has worked on my system (and worked
only) with SPA checked.  See http://support.microsoft.com/kb/287604
[How to configure MSN to work with Outlook] (updated 18 April):

Microsoft Office Outlook 2003 and earlier versions of Outlook
...
b.  In the Incoming Mail Server (POP3) box: type pop3.email.msn.com.
c.  In the E-mail Address box: type your e-mail address, for example,
"myemail@msn.com".
d.  In the Outgoing Mail Server (SMTP) box: type smtp.email.msn.com.
e.  In the User Name box, type your MSN account name.
f.  Click to check the Remember Password checkbox.
g.  In the Password box, type your MSN password.
h.  Click to check the Log on using Secure Password Authentication
(SPA) checkbox.
...
8. On the Outgoing Server tab, click to select the My outgoing server
(SMTP) requires authentication box.
9. Click to select Use same settings as my incoming mail server, and
then click OK.

To me, the odd thing is that, having specified that SPA login is
required, I get no prompt to login (which I always did), just the
error message.  Needless to say, web access to the msn account (mail
and other premium services requiring login) works fine.

Thanks for your help.