// We instantiate the pop3 client.
Pop3Client pop = new Pop3Client();
 
try
{
    this.AddLogEntry(string.Format("Connection to the pop 3 server : {0}", _tbPop3Server.Text));
 
    // Connect to the pop3 client
    pop.Connect(_tbPop3Server.Text, _tbUserName.Text, _tbPassword.Text);
 
    if (pop.MessageCount > 0)
    {
        //Retrive a message at a particulat index
        ActiveUp.Net.Mail.Message message = pop.RetrieveMessageObject(1);
        if (message.HasDomainKeySignature)
        {
            bool signatureValid = message.Signatures.DomainKeys.Verify();
 
            if (signatureValid)
            {
                this.AddLogEntry("The domain key signature is valid.");
            }
            else
            {
                this.AddLogEntry("The domain key signature is invalid.");
            }
        }
        else
        {
            this.AddLogEntry("The message hasn't domain key signature.");
        }
    }
 
    else
    {
        this.AddLogEntry("There is no messages in the pop3 account.");
    }
}
 
catch (Pop3Exception pexp)
{
    this.AddLogEntry(string.Format("Pop3 Error: {0}", pexp.Message));
}
 
catch (Exception ex)
{
    this.AddLogEntry(string.Format("Failed: {0}", ex.Message));
}
 
finally
{
    if (pop.IsConnected)
    {
        pop.Disconnect();
    }
}