POP3Client.GetRawEmail(i, sRawEmail) 'выгружаем наше письмо под номером i = 1 в переменную  sRawEmail 

Dim encode As New System.Text.ASCIIEncoding() 'задаём кодировку, пробовал также UnicodeEncoding, UTF8Encoding, UTF7Encoding, UTF32Encoding.

Dim encodedString() As Byte

encodedString = encode.GetBytes( rawEmailString ) 'кодируем

 rawEmailString  = encode.GetString(encodedString) 'присваиваем переменной  rawEmailString  результат кодировки

Dim ci As System.Globalization.CultureInfo
ci = New System.Globalization.CultureInfo("ru-RU")
System.Threading.Thread.CurrentThread.CurrentCulture = ci
System.Threading.Thread.CurrentThread.CurrentUICulture = ci

Public Sub GetMail(ByVal m_PopServer As String, ByVal m_User As String, ByVal m_Password As String, Optional ByVal m_ServerPort As Integer = 110, Optional ByVal m_useSSL As Boolean = False, Optional ByVal m_DeleteEmails As Boolean = True, Optional ByVal m_SaveDir As String = vbNullString, Optional ByVal m_SaveMailPrefix As String = "MSG", Optional ByVal m_SaveMailExt As String = ".eml", Optional ByVal m_TraceFunction As Pop3.TraceHandler = Nothing, Optional ByVal m_TestMode As Boolean = False)
        Try
            Dim POP3Client As Pop3.cPop3MailClient
            Dim iNumberOfMails As Integer, iMailboxSize As Integer, sRawEmail As String

            'prepare pop client
            POP3Client = New Pop3.cPop3MailClient(m_PopServer, m_ServerPort, m_useSSL, m_User, m_Password)
            POP3Client.IsAutoReconnect = True

            'if tracing needed
            If m_TraceFunction IsNot Nothing Then
                AddHandler POP3Client.Trace, m_TraceFunction
            End If

            POP3Client.ReadTimeout = 60000 'give pop server 60 seconds to answer

            'establish connection
            POP3Client.Connect()

            'get mailbox statistics
            POP3Client.GetMailboxStats(iNumberOfMails, iMailboxSize)

            If m_TestMode Then
                'get a list of mails
                Dim EmailIds As New List(Of Integer)
                POP3Client.GetEmailIdList(EmailIds)

                'get a list of unique mail ids
                Dim EmailUids As New List(Of Pop3.EmailUid)
                POP3Client.GetUniqueEmailIdList(EmailUids)

                'only show info
                If iNumberOfMails > 0 Then
                    For i As Integer = 1 To iNumberOfMails
                        'get email size
                        POP3Client.GetEmailSize(i)
                    Next
                End If

                'ping server
                POP3Client.NOOP()
            Else
                'get emails
                If iNumberOfMails > 0 Then
                    If Strings.Len(m_SaveDir) = 0 OrElse IO.Directory.Exists(m_SaveDir) = False Then m_SaveDir = My.Application.Info.DirectoryPath
                    If Strings.Len(m_SaveMailPrefix) = 0 Then m_SaveMailPrefix = "MSG"
                    If Strings.Len(m_SaveMailExt) = 0 Then m_SaveMailExt = ".eml"
                    If Strings.Left(m_SaveMailExt, 1) <> "." Then m_SaveMailExt = "." & m_SaveMailExt

                    Dim fToSave, encoded As String
                    fToSave = m_SaveDir & "Message" & m_SaveMailExt

                    For i As Integer = 1 To iNumberOfMails
                        'get email size
                        POP3Client.GetEmailSize(i)

                        'get email
                        sRawEmail = ""
                        POP3Client.GetRawEmail(i, sRawEmail)
                        If Strings.Len(sRawEmail) > 0 Then
                            Try
                                encoded = EncodeString(sRawEmail)
                                IO.File.WriteAllText(fToSave, encoded, System.Text.Encoding.ASCII)
                            Catch
                            End Try
                        End If

                        'delete email
                        If m_DeleteEmails Then
                            POP3Client.DeleteEmail(i)
                        End If
                    Next
                End If
            End If

           'close connection
            POP3Client.Disconnect()

            lblMessage.Text = "Было сохранено мейлов: " & iNumberOfMails
        Catch ex As Exception
            If m_TraceFunction IsNot Nothing Then
                m_TraceFunction("Run Time Error Occured:")
                m_TraceFunction(ex.Message)
                m_TraceFunction(ex.StackTrace)
            End If
        End Try

    End Sub