(.NET Core C#) IMAP Download and Verify Signed (S/MIME) Email

Demonstrates how to download and verify digitally signed S/MIME email.

Note: This example requires Chilkat v11.0.0 or greater.

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bool success = false;

// This example requires the Chilkat API to have been previously unlocked.
// See Global Unlock Sample for sample code.

Chilkat.Imap imap = new Chilkat.Imap();

// Connect to an IMAP server.
// Use TLS
imap.Ssl = true;
imap.Port = 993;
success = imap.Connect("imap.example.com");
if (success == false) {
    Debug.WriteLine(imap.LastErrorText);
    return;
}

success = imap.Login("myLogin","myPassword");
if (success == false) {
    Debug.WriteLine(imap.LastErrorText);
    return;
}

// Select an IMAP mailbox
success = imap.SelectMailbox("Inbox");
if (success == false) {
    Debug.WriteLine(imap.LastErrorText);
    return;
}

// We can choose to fetch UIDs or sequence numbers.
bool fetchUids = true;

// Get the message IDs of all the emails in the mailbox
Chilkat.MessageSet messageSet = new Chilkat.MessageSet();
success = imap.QueryMbx("ALL",fetchUids,messageSet);
if (success == false) {
    Debug.WriteLine(imap.LastErrorText);
    return;
}

Chilkat.Email email = new Chilkat.Email();
Chilkat.Cert cert = new Chilkat.Cert();

int i = 0;
while (i < messageSet.Count) {

    string uid = messageSet.GetId(i);
    Debug.WriteLine("uid: " + uid);

    success = imap.FetchEmail(false,uid,true,email);
    if (success == false) {
        Debug.WriteLine(imap.LastErrorText);
        return;
    }

    // The security layers of signed and/or encrypted emails
    // are automatically "unwrapped" when loaded into
    // a Chilkat email object.
    // An application only needs to check to see if an email
    // was received signed or encrypted, and then examine
    // the success/failure.  For example:
    if (email.ReceivedSigned == true) {

        Debug.WriteLine("This email was signed.");

        // Check to see if the signatures were verified.
        if (email.SignaturesValid == true) {
            Debug.WriteLine("Digital signature(s) verified.");
            Debug.WriteLine("Signer: " + email.SignedBy);

            // Get the certificate used for signing.
            success = email.LastSignerCert(0,cert);

            if (success == false) {
                Debug.WriteLine("Failed to get signing certificate object.");
            }
            else {
                Debug.WriteLine("Signing cert: " + cert.SubjectCN);
            }

        }
        else {
            Debug.WriteLine("Digital signature verification failed.");
        }

    }

    i = i + 1;
}

// Disconnect from the IMAP server.
success = imap.Disconnect();