Microsoft is removing TLS 1.0 and 1.1 from Microsoft 365. This has been well flagged, but tenants might not understand the impact on PowerShell scripts which send email using the Send-MailMessage cmdlet and SMTP AUTH. In a nutshell, unless you force PowerShell to use TLS 1.2, attempts to send messages via Exchange Online will fail. It’s time to check those scripts and ,consider how to move away from SMTP AUTH and Send-MailMessage.
https://office365itpros.com/2021/11/12/microsoft-flags-need-upgrade-powershell-scripts-use-tls-12/
