In the past couple of weeks, I've started to get (on a more and more regular basis) errors with sending emails via scheduled subscriptions in SSRS 2016 (on Windows Server 2016). The error I'm seeing is:
ERROR: Error sending email. Exception: System.Net.Mail.SmtpException: Failure sending mail. ---> System.IO.IOException: Authentication failed because the remote party has closed the transport stream.
This doesn't happen every time. For example I've got a report that should have been sent at 1pm - it failed with the above error but as SSRS retries every 15 minutes it actually got sent 30 minutes later.
From what I could find by googling, this might in some way relate to TLS 1.2 - but I can't see anywhere in SSRS where you define what it should use. I upgraded the .NET Framework to 4.8 but that has made no difference.
Any help would be greatly appreciated!