Mail Server Configuration Standards
Essential Pillars of Modern Mail Server Infrastructure
Email deliverability relies on strict adherence to RFC email standards and cryptographic authentication. A misconfigured mail exchanger will cause legitimate emails to be sent to the spam folder or rejected outright.
Standard Mail Ports Tested
- Port 25 (SMTP): The standard port for server-to-server email routing. Must accept connections without blocking from global MTAs.
- Port 587 (Submission / STARTTLS): The modern standard port for client-to-server outbound email submission.
- Port 465 (SMTPS): Implicit TLS submission port widely utilized by email client applications.
Reverse DNS (PTR) Alignment
Major email providers (Google, Microsoft, Apple) mandate Forward-Confirmed Reverse DNS (FCrDNS). The sending IP's PTR record must resolve to a valid hostname, which in turn must resolve back to that same IP address.
❓ Frequently Asked Questions
What happens if my mail server does not have an MX record?
Without an MX record, sending mail servers will attempt to fall back to the root A record. However, modern spam filters often reject or severely delay emails sent to domains lacking explicit MX records.