I send a newsletter to people that subscribe to it. I use my website's server to send the e-mail (from e-mail management software called Interspire), and it uses my e-mail address' SMTP information to send it. A large percentage of the e-mails return with SMTP error 550, mostly from orange.fr, wanadoo.fr, sfr.fr and Hotmail.
I can't figure out what error 550 is supposed to mean. It just says that the message is rejected.
Here is a sample response (with some e-mail addresses removed):
De: Mail Delivery System Objet: Mail delivery failed: returning message to sender Date: 5 août 2015 19:27:05 UTC−4 À: email@example.com This message was created automatically by mail delivery software. A message that you sent could not be delivered to one or more of its recipients. This is a permanent error. The following address(es) failed: firstname.lastname@example.org host smtp-in.orange.fr [126.96.36.199] SMTP error from remote mail server after end of data: 550 5.2.0 Mail rejete. Mail rejected. ofr_506  ------ This is a copy of the message, including all the headers. ------ Return-path: Received: from cloud100.whc.ca ([188.8.131.52]:43757 helo=www.myserver.com) by cloud100.whc.ca with esmtpa (Exim 4.85) (envelope-from ) id 1ZN7ay-00031C-Lc for email@example.com; Thu, 06 Aug 2015 00:55:36 +0200