I think the most support you'd get for sending mail via PHP in production environments is to connect directly to the SMTP server via TCP. This would depend solely on the allow_url_fopen configuration in PHP.ini. This is most likely enabled on any production PHP server.
If it isn't, you could resort to CURL, which would be the alternative given by the hosting if they have turned off allow_url_fopen for some reason.

If you want secure mail transfer, then you'd need to have OpenSSL installed so your TCP connection can be done over TLS or SSL. Some SMTP server may not allow plain-text transfer, which makes TLS support a requirement.