Exchange must have anti-spam filtering enabled.

Originators of spam messages are constantly changing their techniques to defeat spam countermeasures; therefore, spam software must be constantly updated to address the changing threat. Spam protection mechanisms include, for example, signature definitions, rule sets, and algorithms. Exchange 2019 provides both anti-spam and anti-malware protection out of the box. The Exchange 2019 anti-spam and anti-malware product capabilities are limited but still provide some protection.