Part 2: Build multiple mail servers with one domainとドメイン変換技術と詳細なPostfix実装
Deep Mechanisms of Domain Transformation Algorithms
Building on our previous discussion of domain transformation technology, let’s explore the implementation-level details. The innovation of this technology lies in dynamic email address conversion and intelligent routing to appropriate servers.
この技術の重要な点は、Build multiple mail servers with one domainを実現するためのダイナミックなメールアドレス変換と、適切なサーバーへのインテリジェントなルーティングにあります。
In traditional email systems, email addresses in the format user@example.com were delivered only to single server groups specified by DNS MX records. However, our system can branch these email addresses into multiple processing paths the moment they’re received.
The domain transformation process executes through the following steps. First, we analyze incoming email header information to determine sender, recipient, and email content characteristics. Next, we comprehensively analyze factors such as current server load conditions, network status, and recipient geographical location. Finally, we select the optimal processing server and convert the email address to the appropriate server format for forwarding.
Revolutionary Utilization of Postfix Transport Maps
We significantly extended Postfix mail server transport functionality to develop our proprietary Transport Maps system. This enables dynamic destination determination for received emails and optimal server forwarding.
In standard Postfix configurations, transport_maps only referenced static configuration files. However, our system retrieves the latest forwarding destination information from databases or APIs in real-time, dynamically determining routing destinations.
# Basic configuration in main.cf
transport_maps = mysql:/etc/postfix/mysql-transport.cf
# Dynamic transport configuration example
domain.com relay:[dynamic-relay1.domain.com]:25
subdomain.domain.com relay:[load-balanced-relay.domain.com]:25
*.domain.com smart:[intelligent-router.domain.com]:587This configuration enables delivery to different servers even within the same domain, depending on recipients or email content. For example, emails with large file attachments are automatically routed to high-performance servers, while regular text emails go to standard servers.
Implementation of Advanced Load Balancing Algorithms
To achieve efficient load balancing across multiple email servers, we developed and implemented the following advanced algorithms:
Building on round-robin methods, we constructed weighted distribution systems that consider current server load conditions. We monitor each server’s CPU utilization, memory usage, disk I/O status, and network bandwidth usage in real-time, distributing emails to servers that can process them most efficiently.
We also implemented geographical optimization functionality. By analyzing sender and recipient geographical locations, we select servers that minimize network latency. This achieves significant acceleration in international email delivery.
Health check functionality continuously monitors each server’s operational status, automatically excluding failed servers from traffic. During failure recovery, traffic is gradually restored, maintaining overall system stability.
Detailed Security Implementation
Security became paramount when transferring emails between multiple servers. We implemented the following comprehensive security measures:
We developed DKIM (DomainKeys Identified Mail) signature inheritance mechanisms. This technology preserves original sender DKIM signatures while enabling additional signing at relay servers, proving sender legitimacy even after email forwarding.
We implemented extended SPF (Sender Policy Framework) authentication. We developed SPF configurations that legitimize sending from multiple IP addresses, bypassing traditional SPF limitations while maintaining security.
We enforce TLS 1.3 encryption across all relay paths, preventing email content eavesdropping and tampering. We also implemented Perfect Forward Secrecy, strengthening protection against future cryptographic breaches.
Performance Optimization Technologies
To ensure stable operation under high-load conditions, we implemented the following innovative optimization technologies:
Database connection pool optimization significantly reduced connection overhead. We minimized connection creation and destruction costs while improving throughput.
We built in-memory cache systems to store frequently accessed configuration information, routing tables, and user authentication information in memory. This reduced database access frequency and dramatically improved response times.
Asynchronous processing engine implementation enabled email processing parallelization. While traditional synchronous processing required waiting for one email to complete before processing the next, asynchronous processing allows simultaneous parallel processing of hundreds of emails.
Our next article will detail DNS-level implementation methods and domain authentication systems for multi-server integration, including actual configuration examples.
