PHP直接发送原始邮件（eml文件）

I need to send encrypted and/or signed e-mail using CAdES from PHP. For that I have my linux server intercommunicate via a Windows server to generate a S/MIME EML file which conforms to the CAdES standard.

How would I send this mail from PHP ? PHP mail function cannot accept a "raw" mime message and will build a mail from the passed headers. PHPMailer cannot, as far as I know, accept a full raw mail.

Can I somehow inject that mail directly to the MTA? The server might not have sendmail though.

Thanks a lot.