My programmers have written a newsletter program in PHP using the PHP mail function for a client, but when sending the newsletter as HTML, it was received in a mess.
We tested the program on another server and it worked flawlessly.
What was found is that with magic_quotes_gpc being enabled on the server, this was causing the problem. Once the server fellows I hired found this and disabled magic_quotes_gpc, the newsletter program works great.
I am running redhat 7.3 with Exim mail server and CPanel.