空白多部分电子邮件

我正在使用PHP发送一个multipart / mixed消息（纯文本，html和附件）。然而，虽然它适用于大多数帐户，但Yahoo，GMail和Sky似乎显示空白的电子邮件。哪里似乎都显示电子邮件。任何一个帮助都会被很好的认可！

I'm using PHP to send out a multipart/mixed message (plain text, html and attachments). However, whilst it works for most accounts, Yahoo, GMail and Sky seem to show blank emails. Where as everything else seems to display the email. ANY HELP WOULD BE GREATLY APPRECIATED!

我的标题是

$headers .= "Content-Type: multipart/mixed; boundary=\"mixed-" . $random_hash . "-mixed\"\n";
$headers .= "MIME-Version: 1.0\n"; 

内容是;

--mixed-7df05b31-mixed  

Content-Type: multipart/alternative; boundary="alt-7df05b31-alt"  

--alt-7df05b31-alt 

Content-Type: text/plain; charset=utf-8 

            Hello how are you? I am just checking the mailing function.

            Hopefully this will work!

            Cheers.

--alt-7df05b31-alt 

Content-Type: text/html; charset=utf-8 

<div style="font-family:Arial, Helvetica, sans-serif; font-size: 10pt;">

<div> 


            Hello how are you? I am just <b>checking</b> the mailing function.<br><br>


            Hopefully this will work!<br><br>


            Cheers.</div></div>

--alt-7df05b31-alt--

--mixed-7df05b31-mixed 

Content-Type: text/plain; name="abc.txt"  
Content-Disposition: attachment; filename="abc.txt"   
Content-Transfer-Encoding: base64

SEVMTE8gSlVTVCBURVNUSU5HIC4uLiA=

--mixed-7df05b31-mixed--