PHP minimal send mail

Send mail over PHP with minimal requirements from email services

Minimal requirements from email services:

Headers fields:

• Content-type
• Charset
• From
• MIME-Version
• Content-Transfer-Encoding
• Date (in format Fri, 21 Jul 2017 18:05:32 +0200 (CEST))
• Subject (handle this field over iconv_mime_encode)