Cannot send e-mail new SMTP provider

edwinschutten

We want to use a SMTP server from a new provider. When I tried to send a test e-mail I get the error message "Unable to read data from the transport connection: net_io_connectionclosed..".
The provider told me that they use explicit SSL and that probably Business Central (.NET) use implicit SSL.
How do I change this, I can't find a property were I can change implicit/explicit SSL?

kylehardin

What version?

edwinschutten

Microsoft Dynamics 365 Business Central NAV 14.0 (14.0.34251.0)

kylehardin

There isn't a property that controls what type of SSL is used. But I think the port is what controls that. I know Office 365 wants port 587. What port does your provider say you should use?

Here's an article on port 587 versus 25.
https://www.mailgun.com/blog/which-smtp-port-understanding-ports-25-465-587/

Note that this article also shows an example of how you can use telnet from a command line to help troubleshoot. I suspect that either you are using the wrong port, or that authentication is failing, but that is getting reported to you as a connection close error. But you can get BC out of the way and test with a command line.

edwinschutten

The supplier is using port 465. When I use Gmail on port 587 it is working fine. But I think (and also the supplier) that is an implicit/explicit SSL problem.

kylehardin

That is not a setting that BC will let you control. You can go look at the code in C400 SMTP Mail, but all of the heavy lifting is done in a DotNet DLL, not in C/AL or AL.