Some SMTP servers require e-mail eol and eof to be marked with "\r\n", but they are only being marked with "\n". This kills compatibility (and all outgoing e-mail functionality) with those servers.

See a full description of the problem and a sample (minimalistic) fix here: http://www.phpbb.com/community/viewtopic.php?f=46&t=1489875&p=8876785#p8876785

If this is the right approach, the email formatting code should probably be factored into a function.