MSEXchange not rejecting bad email addresses

I have written a specialized email application In ACCES 2010 for my department. At first I couldn't send email outside our domain so the server folks turned on relay and gave me a static IP address. However, now the mail server does not reject bad email addresses unless I leave off everything to the right of the @ sign. Example my real address isme@mycompany.org. But if I change something in the address, such asmexxxx@mycompany.org I don't get an error message back from the mail server, error handling is ignored and it counts as being sent.  This is true for emails going both inside and outside the domain.  It seems to me that something needs to be configured on the host, or I need to do something in my ap. (I'm no expert here.)  The Send part of the code is an ACCESS 2010 function. (Mail server is MSExchange 2010.) If nothing is wrong it works great.

Public Sub SendAMessage(strFrom As String, strTo As String, _
    strSubject As String, strTextBody As String, _
     Optional strAttachDoc As String, Optional strCC As String, _
    Optional strBcc As String)

   
On Error GoTo ErrorHandler

Set objMessage = New CDO.Message

With objMessage
    .From = strFrom
    .To = strTo
    Debug.Print strTo
    If Len(Trim$(strCC)) > 0 Then
        .CC = strCC
    End If
    If Len(strBcc) > 0 Then
        .BCC = strBcc
    End If
   
    .Subject = strSubject
    .TextBody = strTextBody
   
    If Len(strAttachDoc) > 0 Then
        .AddAttachment strAttachDoc
    End If
   
    With .Configuration.Fields
        .Item(CDO.cdoSMTPServer) = "mymail"
        .Item(CDO.cdoSMTPServerPort) = xx
        .Item(CDO.cdoSendUsingMethod) = CDO.cdoSendUsingPort
        .Item(cdoSMTPConnectionTimeout) = xx
        .Update
    End With
    .Send
End With
Set objMessage = Nothing
Dim CurDateTime As DependencyInfo
CDateTime = Now()
Dim AccountNo As String
AccountNo = GBL_Master_Id

If GBL_PostMailSwitch = True Then   'Test if in management and skip the next three statements
Dim SentSql As String
'DoCmd.SetWarnings False
'SentSql = "INSERT INTO SentEmailTbl(Account_Number, Event, DateSent) Values('" & GBL_Master_Id & "', '" & GBL_Event & "', # " & Now() & " #)"
'DoCmd.RunSQL SentSql
'DoCmd.SetWarnings True
End If
Exit Sub
ErrorHandler:

    Dim BadEmSql As String
    Dim emVal As String
   
     'MsgBox "in error Handler" & " " & Err.Number
     'If Err.Number = -2147220977 Or -2147220980 Then
     'MsgBox "Bad email"
     DoCmd.SetWarnings False
     BadEmSql = "INSERT INTO EmErrorsTbl(AccountNo, EmailAddress, ErrNo, ErrMsg, ErrDate) VALUES('" & GBL_Master_Id & "', '" & strTo & "',  '" & Err.Number & "', '" & Err.Description & "','" & GBL_DateSent & "')"
    
     GBL_Rejected = GBL_Rejected + 1
     Forms!EmailForm!emRejected = GBL_Rejected
     DoCmd.RunSQL BadEmSql
     DoCmd.SetWarnings True
    'End If
      Resume Next
End Sub

Thanks in advance