I'm using sp_send_dbmail to send mails to an Office 365 account. All mails have similar content and are sent to users in the same domain. All mails were sent using the same profile.
About 50% of the mails were delivered and the rest failed to be sent. (Checked in the msdb.dbo.sysmail_allitems), the error is "The mail could not be sent to the recipients because of the mail server failure. (Sending Mail using Account 9 (2022-01-28T17:38:08). Exception Message: Cannot send mails to mail server. (Failure sending mail.).)"
Does anyone have an idea what could cause this error?
I sent this just before my weekend, I will be back to check on Monday.