Exchange Web Service API and 401 unauthorized exception

Question

When I try sending email using the EWS API, I get the following error: (in message.Send();)

The request failed. The remote server returned an error: (401) Unauthorized.

My code is the following:

ExchangeService exchangeService = new ExchangeService(ExchangeVersion.Exchange2007_SP1);

//WebService Uri
try
{
    exchangeService.Url = new Uri("https://exchangeserver/ews/exchange.asmx");
}
catch (Exception ex)
{
    throw new Exception(string.Format("WebService Uri:" + ex));
}

//Credentials
try
{
    exchangeService.Credentials = new WebCredentials("user@domain", "pwd", "domain");
}
catch (Exception ex)
{
    throw new Exception(string.Format("Credentials:" +  ex));
}

//Send a mail
try
{
    EmailMessage message = new EmailMessage(exchangeService);
    message.Subject = "Test";
    message.Body = "Test";
    message.ToRecipients.Add("destination@domain");
    message.Save();
    message.Send();
}
catch (Exception ex)
{
    throw ex;
}

I read other posts on this site concerning this issue but they couldn't resolve my issue.

Answer 1

Try changing this:

 exchangeService.Credentials = new WebCredentials("user@domain", "pwd", "domain");

into this:

 exchangeService.Credentials = new WebCredentials("user", "pwd", "domain");

Sometime the Login credentials depends on how Exchange/Active Directory it's configured. It could be user@domain or domain\user