I use CentOS server with Postfix for mail sendind and my PHP application use mail(0 for mail sending.
Some "FAQ" problem with this setup have been solved quickly using Google (e.g. passing "From" field through additional sendmail arguments rather than as additional header), but i still have one with DKIM milter.
As I see, it doesn't proper include some headers into signature. It works good with "Reply-To" header, but if I pass "List-Unsubscribe" header to mail() Gmail.com and Yandex.ru mail servers mark my mails as spam after DKIM check.
How can I solve this problem?