This means the SMTP (outbound) server you're connecting to wants a username
& password to let you send mail through it - very common given the number of
spammers who would love to send mail through an open relay server. Contact
your ISP/mail host for more info, but in general, the option to authenticate
is in your mail account properties - you haven't mentioned your v. of
Outlook, which makes a big difference. Look around; you should find it. The
login info is usually your same POP account credentials, presuming you're
sending mail through your mail host's SMTP server & not someone else's.
It's on the Outgoing Server tab of your account properties pages. Exactly
what to click to find it is dependent on your version of Outlook and you
decided to keep that a secret.
