SMTP requires authentication

Can anyone tell me why Outlook 6 in XP Home, when DSL connected to an ISP, needed to have SMTP “authenticated” but nothing regarding the “POP” side of the transaction?

I didn’t install the “nifty” software that the ISP sent (it’s really awful) so maybe that’s it?

Interstingly, once I chose the checkbox “my outgoing mailserver requires authentication” .. all is well >??

AnswerMan