Success! I finally found a combination that worked. Thought I'd pass this on in case others run into this MSN problem. I rechecked name and password for spelling, the correct port addresses and settings that you mentioned, etc. First, msn wants the whole correct email address, not just the prefix. But the weird setting is to check the "Disable certificate validation" box... for both the POP3 and SMTP security settings. I wouldn't 'o thunk it!
Now do you know where I can get a list of file names that Pegasus uses, so I can copy them onto a different computer with a newly installed Pegasus, so they have the same folders, addressbooks, and setups?
In any case, thanks to all who contributed to unraveling my dilemma. I am happy to continue to use Pegasus.