public event ErrorEventHandler ErrorOccurred

Public Event ErrorOccurred As ErrorEventHandler

using System;
using MailBee;
using MailBee.Pop3Mail;

class Sample
{
    // ErrorOccurred event handler.
    private static void OnErrorOccurred(object sender, ErrorEventArgs e)
    {
        // Check whether the error is critical or not.
        if (e.IsFinalError)
        {
            // Display corresponding MailBeeException.Message.
            // After OnErrorOccurred handler finishes, MailBee will 
            // throw the same exception to the application code.
            Console.WriteLine("CRITICAL ERROR: " + e.Reason.Message);
        }
        else
        {
            // Display corresponding MailBeeException.Message.
            // After OnErrorOccurred handler finishes, MailBee will 
            // try another methods to accomplish the current task.
            Console.WriteLine("WARNING: " + e.Reason.Message);
        }
    }

    // The actual code.
    static void Main(string[] args)
    {
        Pop3 pop = new Pop3();

        // Subscribe to the ErrorOccurred event.
        pop.ErrorOccurred += new ErrorEventHandler(OnErrorOccurred);

        // Connect to the server.
        pop.Connect("mail.domain.com");

        // Request any data which needs CAPA command to be issued 
        // in order to obtain the required information. The list of supported 
        // authentication methods can serve this purpose. If CAPA command 
        // fails (but the server responds, i.e. the connection itself is still valid),
        // MailBee will not throw any exception to the application code  
        // (but ErrorOccurred event will still be raised) and will try to issue 
        // AUTH command to get the list of supported authentication methods.
        // If AUTH command fails too, it's still not a critical error. SASL 
        // authentication methods will just not be available.
        AuthenticationMethods authMethods = pop.GetSupportedAuthMethods();

        // Close the connection
        pop.Disconnect();
    }
}

Imports System
Imports MailBee
Imports Pop3Mail

Public Class Sample
    ' ErrorOccurred event handler.
    Private Shared Sub OnErrorOccurred(ByVal sender As Object, ByVal e As ErrorEventArgs)
        ' Check whether the error is critical or not
        If e.IsFinalError Then
            ' Display corresponding MailBeeException.Message.
            ' After OnErrorOccurred handler finishes, MailBee will 
            ' throw the same exception to the application code.
            Console.WriteLine("CRITICAL ERROR: " & e.Reason.Message)
        Else
            ' Display corresponding MailBeeException.Message.
            ' After OnErrorOccurred handler finishes, MailBee will 
            ' try another methods to accomplish the current task.
            Console.WriteLine("WARNING: " & e.Reason.Message)
        End If
    End Sub

    ' The actual code
    Shared Sub Main(ByVal args As String())
        Dim pop As New Pop3

        ' Subscribe to the ErrorOccurred event.
        AddHandler pop.ErrorOccurred, AddressOf OnErrorOccurred

        ' Connect to the server.
        pop.Connect("mail.domain.com")

        ' Request any data which needs CAPA command to be issued 
        ' in order to obtain the required information. The list of supported 
        ' authentication methods can serve this purpose. If CAPA command 
        ' fails (but the server responds, i.e. the connection itself is still valid),
        ' MailBee will not throw any exception to the application code 
        ' (but ErrorOccurred event will still be raised) and will try to issue 
        ' AUTH command to get the list of supported authentication methods.
        ' If AUTH command fails too, it's still not a critical error. SASL 
        ' authentication methods will just not be available.
        Dim authMethodrs As AuthenticationMethods = pop.GetSupportedAuthMethods()

        ' Close the connection.
        pop.Disconnect()
    End Sub
End Class