PHP has a mail() funcition which you can use to send either plain text or HTML text.
To send HTML text you need to include special header info in the function

Syntax: mail(to, subject, message, headers, parameters);

Parameter Description
to Required. Specifies the receiver / receivers (semicolon delimited) of the email
subject Required. Specifies the subject of the email. Note: This parameter cannot contain any newline characters
message Required. Defines the message to be sent.
Note:
  • For Plain text - Each line should be separated with a LF (\n). Lines should not exceed 70 characters
  • For HTML text - use normal HTML tags.
    		•
    headers Optional. Specifies additional headers, like From, Cc, and Bcc. The additional headers should be separated with a CRLF (\r\n)
    parameters Optional. Specifies an additional parameter to the sendmail program

    For Example:
    $to= $addy;
    $subject ="My mailing thingy";
    $headers = "From: me@myaddy.com";
    $message ="This is my message\n\rNOTE: that I am using newline and return code as the headers do not specify text/html.";
    mail ($to,$subject,$message,$headers);

    To send text in HTML create headers as in this example:
    $headers = "MIME-Version: 1.0\r\n";
    $headers .= "Content-type: text/html; charset=iso-8859-1\r\n";
    $headers .= "From: me@isp.com\r\n";

    If you use this last method, then the message MUST be in html code, not Unix style text code. Therefore use <p> for paragraphp spacing not \n\r