We have a SQL Server 2016 Standard Edition. I set up the SQL mail service (account + profile) on it a year ago, which worked perfectly (account: smtp.office365.com:587, SSL, basic auth).
Since October 11, 2021, there have been constant problems with sending mail. In many cases, sending mail doesn't work, I get the following error message:
The mail could not be sent to the recipients because of the mail server failure. (Sending Mail using Account 3 (2021-10-27T18: 07: 10). Exception Message: Cannot send mails to mail server. (Failure sending mail.).)
Here is an excerpt from the sysmail_allitems table:
I don't understand what the problem is because the server sends the email once but not the other time.
Do you have any idea what might be causing the problem?