Enterprise Email Infrastructure: Security Baseline and Best Practices - ARC SEAL

Authenticated Received Chain (ARC) Seal

ARC Seal is an email authentication mechanism that preserves email authentication results across multiple intermediaries, such as forwarding services and mailing lists. It allows the authentication status of an email to be reliably transmitted even if the email passes through multiple hops.

Benefits:
- Maintains email authentication results through intermediaries
- Ensures consistent email authentication
- Helps prevent false positives in email filtering

Implementation:
1. Enable ARC on your mail servers.
2. Ensure that ARC seals are added to outgoing emails and validated on incoming emails.

Mail Transfer Agent Strict Transport Security (MTA-STS)

MTA-STS is a security protocol that enables email service providers to ensure emails are only sent using encrypted channels, helping to prevent downgrade attacks and man-in-the-middle attacks.

Benefits:
- Enforces the use of TLS for email transmission
- Protects against man-in-the-middle attacks
- Ensures the privacy and integrity of email communications

Implementation:
1. Publish an MTA-STS policy in your DNS settings.
2. Create an MTA-STS policy file and host it on your web server.
3. Configure your mail servers to enforce the MTA-STS policy.