First of all, you might have an email address. Not an Outlook mail address
Second of all, why do you think they actually used your email address to actually sent the spam? They just used your name, not your account.
To make this a bit easier to understands lets consider paper mail:
- I can type a spam/ad and put it in an envelope.
- On the front of the envelope I write the destination.
- On the rear of the envelope I write the senders (my) address, it case it can not be delivered and it has to be returned.
There is nothing which prevent me from writing your address on the back of my envelopes.
Similarly, there is nothing which prevents me doing that with electronic mail.
No security flaws or compromised servers are needed.
1Sorry I meant a hotmail adress (which is now Outlook -not the software-) What makes me thinks they used my email is that I received an official email from microsoft (delivery failure) plus i have discovered multiple SENT emails in my sent folder (all spams) – Vincent – 2013-08-08T17:50:51.827
Could you edit your original post to include this information? It is more likely to be read there than in the comments on one (and hopefully later multiple) answers. – Hennes – 2013-08-08T18:01:11.727