‘Autodiscover service couldn’t be located’ when trying to access Exchange 2010 account with EWS MANAGED API

You got Service.Credentials wrong, use it like this:

Service.Credentials = new WebCredentials(username, password, domainname);

Using domain credentials, not the email address.

Also doublecheck the following:

1. The version you specify in new ExchangeService() matches server’s
2. the parameter passed to Service.AutodiscoverUrl(); is correct (email address which data needs to be fetched)

The following works for me (in a new Console Application):

// Tweaked to match server version
ExchangeService Service = new ExchangeService(ExchangeVersion.Exchange2007_SP1); 

// Dummy but realistic credentials provided below
Service.Credentials = new WebCredentials("john", "12345678", "MYDOMAIN");
Service.AutodiscoverUrl("john.smith@mydomain.it");
Folder inbox = Folder.Bind(Service, WellKnownFolderName.Inbox);
Console.WriteLine("The folder name is " + inbox.DisplayName.ToString());

//Console output follows (IT localized environment, 'Posta in arrivo' = 'Inbox')
> The folder name is Posta in arrivo