Recently I ran into a problem, when sending gMail messages (and others too), could not correctly display my letter written by Cyrillic.
Climbed on the Internet, there this question has already been raised, and a solution was proposed. After reworking it for myself, I decided to put it here too. I think that some of you may find it useful too:
// The trim function removes spaces at the beginning and end
$ title = htmlspecialchars (trim ($ _ POST ['title']));
$ mess = htmlspecialchars (trim ($ _ POST ['mess'));