I always install "locate" and whenever I change anything do as root "/usr/bin/updatedb" then you can type "locate *.log"
Thank you. It worked and I now have several log files to check.
In the meantime, I've tried once again to send a message to "mailtest" from an outside address; this time, I got an error reply:
This report relates to a message you sent with the following header fields:
Message-id: 00e201d2290f$67da8c70$378fa550$@mac.com Date: Tue, 18 Oct 2016 09:15:21 +0200 From: Moi To: 'Mail Test' mailtest@barbu.sytes.net Subject: Test
Your message cannot be delivered to the following recipients:
Recipient address: mailtest@barbu.sytes.net Reason: Illegal host/domain name found <end of reply>
Yet another area with a problem; at least this is now a valid reason for it to not work. Is this a misconfiguration of my DNS server?