I am writing an application that has to send some emails. After testing for quite some time i have found the following:
My System.Net.Mail based mail solution doesn't work. The error i get from the mail server is:
Unable to read data from the transport connection: net_io_connectionclosed.
Tested by using Telnet running on the same server as my application and then everything works!
My colleague suggested to test a copy of my solution, converted to using System.Web.Mail. And this solution works!
Could it be that this specific mailserver has problems connecting/accepting mail from the System.Net.Mail component? For now, all i know is that it's a machine running on CentOs.