This is the Postfix program at host gamma.utc.fr.

I'm sorry to have to inform you that the message returned
below could not be delivered to one or more destinations.

For further assistance, please send mail to <postmaster>

If you do so, please include this problem report. You can
delete your own text from the message returned below.

The Postfix program

<john@utc.fr>: host kappa.utc.fr[193.55.117.100] said: 550 <john@utc.fr>: User
unknown in local recipient table (in reply to RCPT TO command)