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
Basic phishing emails are so effective that most hackers don't use exploit kits anymore.
It becomes very easy to spread virus ransomware if your mail servers are not protected, even with Office 365 and Exchange OnLine.
During some automatized deployments, as often, we have to deploy Microsoft Exchange 2016 automatically.