You mean these settigs..? (These are mine, not my colleague's)

Thanks for tips, but everyone he send mail to experience the same problem, so the problem can't be in receivers end. He has deleted the acount several times, and added it again. Same problem each time. I have sent the question to our webhotel/mailserver too, but I don't think the problem are there.

Mail sent from iPhone (5S) or iPad; address turns into rubbish. See image. It is the same whoever he send to. I'm not a Appleguy. I ask for a friend that is. He don't know much about his data equipment. When he send me mail from his iMac, the problem don't occur.