Office365 is no longer allowing my C# app to log into the mailbox via the EWS API. Has this library been deprecated? This fails:
ExchangeService service = new ExchangeService(ExchangeVersion.Exchange2013_SP1);
The error I get when trying is
Exception thrown: 'Microsoft.Exchange.WebServices.Data.ServiceRequestException' in Microsoft.Exchange.WebServices.dll
Additional information: The request failed. The underlying connection was closed: An unexpected error occurred on a send.
I was told they are no longer accepting connections from anything older than 16.0.4600.1000, which is Office 2016.
Does this make any sense? It fails from multiple hosts at different sites, so I know it's not related to the network on our side.