SmimeSign Method (MailMessage, Certificate, CertificateCollection)
Signs an e-mail message with a digital signature, with the ability to provide a user-defined chain of signing certificates.

Namespace: MailBee.Security
Assembly: MailBee.NET (in MailBee.NET.dll) Version: 12.5.0 build 687 for .NET 4.5
Syntax
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public MailMessage Sign(
	MailMessage message,
	Certificate signingCert,
	CertificateCollection extraCerts
)

Parameters

message
Type: MailBee.MimeMailMessage
The original e-mail message to be signed.
signingCert
Type: MailBee.SecurityCertificate
The certificate to be used for signing the message. This certificate must contain a private key.
extraCerts
Type: MailBee.SecurityCertificateCollection
The additional certificates in the chain of the signing certificate. If a null reference (Nothing in Visual Basic), MailBee will build the certificate chain from the signing certificate to the root authority automatically.

Return Value

Type: MailMessage
A reference to the signed message if the signing went successfully; a reference to the original message if it was already signed; a null reference (Nothing in Visual Basic) if the signing process failed.
Exceptions
ExceptionCondition
MailBeeInvalidArgumentExceptionmessage or signingCert is a null reference (Nothing in Visual Basic).
MailBeeSmimeWin32ExceptionA cryptographic error occurred and ThrowExceptions is true (.NET Core 1.0/1.1 edition).
MailBeeCertificateExceptionA cryptographic error occurred and ThrowExceptions is true.
Remarks
This is a special overload which makes it possible to sign e-mail messages with certificate whose root authority certificate is not present in the system store. In this case, extraCerts collection must contain all certificates signingCert derives from (such as root authority and CA certificates).
Examples
The following code snippet demonstrates how to supply a custom certificate chain from a PFX file when signing a message. It's assumed the PFX contains 3 certificates - root authority, intermediate CA, and the signing certificate itself (root certificate being the first in the collection). For a sample on S/MIME signing in general, see Sign(MailMessage, Certificate) topic.
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X509Certificate2Collection certsFromPfx = new X509Certificate2Collection();
certsFromPfx.Import(@"C:\Temp\cert.pfx", "password", X509KeyStorageFlags.PersistKeySet);
CertificateCollection extraCertsForSigning = new CertificateCollection();
extraCertsForSigning.Add(new Certificate(certsFromPfx[1]));
extraCertsForSigning.Add(new Certificate(certsFromPfx[0]));
MailMessage signedMessage = smime.Sign(msg, new Certificate(certsFromPfx[2]), extraCertsForSigning);
See Also