It looks like Outlook is sending multiple spam e-mails to people I do not
know when I send out an a-mail.

I'm guessing this is the case because I am getting 10-20 a-mails a day
saying that unknown addressees I do not recognize cannot accept my mail.
Already my service provider sent a warning and forced me to change from the
"normal" SMTP port to the 587 one. Three questions....

How can I be sure I am attaching spam to my outgoing e-mails. i.e.. the spam
e-mails I receive are in fact true.
How could I see/get to the spam e-mail list
How can I cleanup the problem. I use AVG it detects nothing.