Hello,
One of our customers wants to switch his email delivery to Exchange Online. However, when sending the test email in the SMTP setup, he received the following message:
"The mail system returned the following error: "Error sending mail. Authentication failed because the other party closed the transport stream."
After some Googling, I came to the solution of specifying TLS version 12 explicitly in the code via the following line in the TrySend function in the CU400
ServicePointManager.SecurityProtocol := 3072; // 3072 = Tls12 (TLS 1.2)
It works this way, but I don't really like it because...
- this forces me to use a specific TLS version, which is not recommended by Microsoft. However, it doesn't say how I read the TLS version from the operating system.
- I "mess up" a standard object. Unfortunately, the CU400 does not seem to offer any events in this version that you could subscribe to
Does anyone here know a slightly smoother solution?