Public Function Encrypt(UnEncrypted As String, ByVal iEncrypt As Integer) As _
  String
    Dim cnt As Long, NewChr As Long
    For cnt = 1 To Len(UnEncrypted)
        NewChr = Asc(Mid$(UnEncrypted, cnt, 1)) + iEncrypt * 30
        If NewChr > 255 Then
            Do: NewChr = NewChr - 256: Loop Until NewChr < 255
        ElseIf NewChr < 0 Then
            Do: NewChr = NewChr + 256: Loop Until NewChr > 0
        End If
        Mid$(UnEncrypted, cnt, 1) = Chr$(NewChr)
    Next cnt
    Encrypt = UnEncrypted
End Function

Dim strPassword as String
strPassword=Encrypt(Me.txtSMTPpassword, 1)
' ...... hier der Code zum Speichern in der Datenbank
strPassword = vbNullString

Dim strPassword as String
' .... hier der Code zum Auslesen aus der Datenbank
strPassword=Encrypt(Me.txtSMTPpassword, -1)
strPassword = vbNullString