MS Exchange not accepting email connections from Nop v4.0

Hi,
Can someone help me please. We have recently had to switch our email hosting to MS Exchange, and since then NopCommerce isn't sending emails when a customer places an order. I have tried using ports 587, 465 and 25, and with SSL selected and unselected, but the error returned is the same:

Error in processing. The server response was: 5.7.3 STARTTLS is required to send mail [CH0PR03CA0041.namprd03.prod.outlook.com 2023-05-19T11:23:44.408Z 08DB576FB02CD70F]

Host setting is:  smtp.office365.com

Can anyone tell me what I need to do to get my email working again?
Thank you

See if this helps
https://www.nopcommerce.com/en/boards/topic/82081/cannot-get-ms-outlook-to-send-emails-from-nop-admin-panel

Are you able to send a Test message from the email setup page?

Thanks, I’ll look into that. No, I can’t send a test message - that error message is what I get when I try to send it.

The only workaround the link offered was to disable MFA, which I am not willing to do. Do you have any other suggestions?
Thanks