send PHP mail with Content-Type: multipart/alternative

Question

I am trying to send a multipart mail that contains both html and plain text. This is also one of the ways to get through spam filters and to allow more people to read the ma

Answer 1

The line:

$header .= 'Content-type: multipart/alternative;boundary=$boundary '."\n";

Has the wrong quotes, so $boundary won't be expanded. Change to:

$header .= "Content-type: multipart/alternative;boundary=$boundary\n";

And like I said in the comments, in the message headers and the content section headers you should be using \r\n as the line break since that's what is defined in the RFC. Most MTAs will allow simply \n, but some will choke on the message, and some spam filters will count every RFC violation as a point towards your spam score.

Using something like PHPMailer is a much better option because it formats everything perfectly by default, and abides by just about every single obscure, boring RFC.