When configuring your email settings for Dynamics CRM, make sure you configure Serverside Sync.
As per CRM Tip of the Day https://crmtipoftheday.com/979/start-planning-farewell-party-for-email-router/, the CRM Email router is to be deprecated. You should use the Serverside Sync now instead.
❌ Figure: Bad example - Deprecated Mail routed Enabled
✅ Figure: Good example - Serverside Sync configured as per Connect Dynamics 365 to POP3/SMTP servers
Learn more on Connect Dynamics 365 to POP3/SMTP servers.