Send s/mime multipart/signed email message.

[Casper Hansen]

I need to send a multipart/signed email with detached signature.
The problem is, that I cannot figure out which alternativeview to use.



I have constructed the email so it looks like this (part of the signature is removed):

Content-Type: multipart/signed; protocol="application/pkcs7-signature"
micalg=sha1; boundary="--PTBoundry=3"

----PTBoundry=3
Content-Type: multipart/mixed;
boundary="--PTBoundry=2"

----PTBoundry=2
Content-Type: text/plain; charset="iso-8859-1"
Content-Transfer-Encoding: quoted-printable

TEST AF signed
----PTBoundry=2
Content-Type: application/octet-stream;
name="test.txt"
Content-Transfer-Encoding: base64
Content-Dis;
filename="test.txt"

bWludGVzdGF0dGFjaG1lbnRzaWduZWQ=
----PTBoundry=2--

----PTBoundry=3
Content-Type: application/pkcs7-signature; name="smime.p7s"
Content-Transfer-Encoding: base64
Content-Dis; filename="smime.p7s"

MIIMIQYJKoZIhvcNAQcCoIIMEjCCDA4CAQExCzAJBgUrDgMCGgUAMIIBrgYJKoZIhvcNAQcBoIIB
/2kbmx/g/Dkp9xuEArLxix645wcSlnCh0NUOPBte6w==

----PTBoundry=3--



I have tried sending this using:

var contentType = new ContentType("application/pkcs7-mime; smime-type=signed-data; name=smime.p7s");
var stream = new MemoryStream(message);
var view = new AlternateView(stream, contentType);
message.AlternateViews.Add(view);

however it is not correct and outlook wrties the following error message: "Cannot open this item. Your digital ID name cannot be found by the underlying security system."

How do I add this as an alternativeview correctly?

The mime header should appear as below, but I have not been able to figure out how to do this.

Content-Type: multipart/signed;
boundary="--PTBoundry=3";
protocol="application/pkcs7-signature"; micalg=sha1

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