EMail addresses from Address Book to Mail

Hello folks,
Based on previous guidance, I exported the Outlook Express Address Book as
a *.csv file.
It was created by Excel 2003 for Windows XP and I can open it with Excel for Mac, but curiously nor Mail, nor the Agenda, neither Entourage recognize the file as a *.csv.
I tried to "deceive" the iMac openning the file with Excel for Mac and saving from this application a new *.csv file, but it didn't help either.

Any suggestions? Thanks

To whom it may be of interest
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PMV