Do you know that Microsoft will enforce all privileged Azure AD accounts to use Multi Factor Authentication in march?
It was announced in june 2018. Be prepared for that: Global administrator, SharePoint administrator, Exchange administrator, Conditional access administrator, Security administrator are concerned
When you have multiple Microsoft Exchange Servers receiving emails, you have to create exactly the same receive-connectors.
And that begins to be a nightmare when you have multiple incoming smtp relays with dedicated IP addresses