Using WP 2.8.5
Some providers are protected from the use of injections in the mail function. So, they’re generating an error when Subject string is malformed (with more than 1 line in string).
I’ve got traced an error up to class-phpmailer.php. There are a lot of lines with same code:
@mail($to, $this->EncodeHeader($this->SecureHeader($this->Subject))…
Solution is replace EncodeHeader and SecureHeader with each other places:
@mail($to, $this->SecureHeader($this->EncodeHeader($this->Subject))…
This solution works for me.
You can check this solution easely. Just remove @ symbol from @mail function, so you’ve gotta an errors like this:
Fatal error: mail() [<а hrеf='function.mail'>function.mail]: mail() - newline in Subject, possible injection, mail dropped in /home/httpd/vhosts/.../mail.inc on line 193
If not, then this solution is not for you.