to Russ:

I had only a hotmail.com account, then activated a telenet.be account. When
I receive a message on it, and click the appropriate button, it will say
"this is not an Outlook contact" and when I click "add to contacts" the
sender's name will go into the new contact list. This also happens to senders
who are present on my original contact list with their various e-mail
addresses.

Is does not seem efficient to maintain duplicate Outlook files with each of
my e-mail accounts, but I don't know how & where to start combining.

PS I am an absolute Outlook beginner and do not know what a transport is.