We are currently using SQL Server 2016, which is hosted on Windows Server 8 (2016). According to our company's policy, we have to transition our Windows server to TLS 1.2 before June 2020. After transitioning, we noticed that our database mail has stopped sending alerts.
We are instead given the error in the Mail Log:
The mail could not be sent to the recipients because of the mail server failure. (Sending Mail using Account 1003 (2020-04-20T07:01:28). Exception Message: Cannot send mails to mail server. (Failure sending mail.).
Our database mail account has SSL enabled and uses Basic Authentication. We are connected to port 587 of the smtp.office365.com mail server.
We've also made sure that the SQL Server is up to date with the latest cumulative update.