Unable to initialize ExchangeService instance

The 401 error suggests an authentication issue. Check the following:

Ensure CREATOR_MAIL and CREATOR_PASSWORD are correct.
Set UseDefaultCredentials to false.
Confirm the EXCHANGE_URL is correct or use AutodiscoverUrl with a valid callback.
Verify you have the necessary permissions for impersonation.
Here's a refined initialization:

csharp
Copy code
private static void initExchangeService()
{
m_ExchangeService = new ExchangeService();
m_ExchangeService.UseDefaultCredentials = false;
m_ExchangeService.KeepAlive = true;

string domain = ConfigurationManager.AppSettings["Domain"];
m_ExchangeService.Credentials = new System.Net.NetworkCredential(CREATOR_MAIL, CREATOR_PASSWORD, domain);
m_ExchangeService.ImpersonatedUserId = new ImpersonatedUserId(ConnectingIdType.SmtpAddress, CREATOR_MAIL);
m_ExchangeService.Url = string.IsNullOrEmpty(EXCHANGE_URL) ? new Uri(EXCHANGE_URL) : m_ExchangeService.AutodiscoverUrl(CREATOR_MAIL);

writeToLog($"Initialized exchange service for {CREATOR_MAIL}", MESSAGE);
}
Ensure the network allows the connection and there's no firewall blocking it.