Hello Thomas,
It seems the address in the certificate does not match to the inbound and/or outbound addresses in your account settings.
Re this problem you can check:
http://www.msfn.org/board/topic/9989...-outlook-2007/
http://www.daniweb.com/hardware-and-...curity-warning

The first thing i would suggest trying is the fix in the 2nd link.
Check what are the in/out addresses:
Quoted from the 2nd link:
"If you have AOL and had outlook configure it for you then you probably have the same problem, just go to aol site and find the correct incoming and outgoing mail server and change the settings in outlook."
here is the link how to access in/out settings:
http://www.wiseinternet.com.au/suppo...-Settings.aspx

Kind regards,
Wries