I am using the exact same script you posted. Just added the line to add the envelope-to: header:
$mime->address_headers['envelope-to:'] = 1;
Here is the output of your script. As you may see it shows the address in that header:
Message structure
Array
(
[Headers] => Array
(
[return-path:] =>
[envelope-to:] =>
[email protected]
[delivery-date:] => Thu, 26 Feb 2009 15:24:37 -0600
[received:] => Array
(
[0] => from exprod5mx233.postini.com ([64.18.0.119] helo=psmtp.com)by server.athenshosting.com with smtp (Exim 4.69)(envelope-from )id 1Lcnif-0002oN-1gfor
[email protected]; Thu, 26 Feb 2009 15:24:37 -0600
[1] => from source ([76.96.62.40]) by exprod5mx233.postini.com ([64.18.4.10]) with SMTP;Thu, 26 Feb 2009 13:24:36 PST
[2] => from OMTA09.westchester.pa.mail.comcast.net ([76.96.62.20])by QMTA04.westchester.pa.mail.comcast.net with comcastid LcSx1b0010SCNGk54lQcoJ; Thu, 26 Feb 2009 21:24:36 +0000
[3] => from sz0023.wc.mail.comcast.net ([76.96.58.71])by OMTA09.westchester.pa.mail.comcast.net with comcastid LlQc1b00F1YCShG3VlQczp; Thu, 26 Feb 2009 21:24:36 +0000
)
[date:] => Thu, 26 Feb 2009 21:24:36 +0000 (UTC)
[from:] =>
[email protected]
[to:] =>
[email protected]
[message-id:] => <2001997222.2599081235683476676.JavaMail.root@sz0023a.westchester.pa.mail.comcast.net>
[subject:] => Test
[mime-version:] => 1.0
[content-type:] => multipart/alternative; boundary="----=_Part_130292_1857685444.1235683476675"
[x-originating-ip:] => [66.222.12.253]
[x-mailer:] => Zimbra 5.0.11_GA_2730.RHEL5_64 (ZimbraWebClient - IE6 (Win)/5.0.11_GA_2730.RHEL5_64)
[x-pstn-neptune:] => 0/0/0.00/0
[x-pstn-levels:] => (S:99.90000/99.90000 CV: 0.5996 FC:95.5390 LC:95.5390 R:95.9108 P:95.9108 M:97.0282 C:98.6951 )
[x-pstn-settings:] => 5 (2.0000:2.0000) s CV gt3 gt2 gt1 r p m c
[x-pstn-addresses:] => from [15/1]
)
[Parts] => Array
(
[0] => Array
(
[Headers] => Array
(
[content-type:] => text/plain; charset=utf-8
[content-transfer-encoding:] => 7bit
)
[Parts] => Array
(
)
[BodyPart] => 1
[BodyLength] => 24
)
[1] => Array
(
[Headers] => Array
(
[content-type:] => text/html; charset=utf-8
[content-transfer-encoding:] => 7bit
)
[Parts] => Array
(
)
[BodyPart] => 2
[BodyLength] => 182
)
)
[ExtractedAddresses] => Array
(
[return-path:] => Array
(
[0] => Array
(
[address] =>
[email protected]
)
)
[envelope-to:] => Array
(
[0] => Array
(
[address] =>
[email protected]
)
)
[from:] => Array
(
[0] => Array
(
[address] =>
[email protected]
)
)
[to:] => Array
(
[0] => Array
(
[address] =>
[email protected]
)
)
)
)