To whitelist KnowBe4 servers in Trend Micro Email Security Standard, follow these steps:

1. Go to 'Inbound Protection'.
2. Select 'Domain-based Authentication'.
3. Select 'DMARC'.
4. Select 'Default Domain'.
5. Select 'Ignored Peers'.
6. Add '*.psm.knowbe4.com'.

By following these steps, KnowBe4 Servers will be whitelisted in Trend Micro Email Security Standard, allowing for uninterrupted communication between the two systems.