I solved my problem myself without your help. You are liars , there is no support , just a robots Waltz. I host four sites with Dreamhost . The two I have activated fail to use the WordPress function wp_mail . One uses only the files and the default Wordpress theme : the explanation therefore can not be a conflict of plugins or improper theme.
I tested the functioning of wp_mail with a script found on this site : Mails are not sent. I think it is clear Dreamhost has blocked the function. They do not even read the messages you send: for them my domain is blocked ( by Martians perhaps? ). They have the server logs : I only sent a few emails on my Hotmail account for a test.
Besides, if I can exchange messages using my domain webmail, : that means that I am not blacklisted ! I finally came to pass my mails configuring an SMTP server. without . .. and it is not thanks to Dreamhost. They just sent me a message telling me that there has never been a problem since I started sendig some mails.
It turnsout that I am still in may trial period , I am seriously considering to get refund.