For many businesses, engaging with prospects via email is a critical part of their operations. Delivering their messages can become more challenging as their cold outreach strategy scales. The good news is they can set up their email infrastructure to help with their deliverability woes. Next, you need to choose the right mail transfer agent. In the battle of Postfix vs Sendmail, which one wins? This article will help you confidently select the best MTA for your cold email needs by exploring the differences between Postfix and Sendmail, including performance, security, and ease of configuration with cold email tips.

Inframail’s email infrastructure solution can help you achieve your goals by ensuring your cold email infrastructure is set up for deliverability.

Table of Contents

• What are Sendmail and Postfix and Their Key Capabilities

• In-Depth Postfix vs. Sendmail Mail Transfer Agent Comparison

• Start Buying Domains Now and Setup Your Email Infrastructure Today

What are Sendmail and Postfix and Their Key Capabilities

Sendmail and Postfix are Mail Transfer Agents that help with email delivery. Sendmail was created in the early 1980s by Eric Allman as part of a project for UC Berkeley. It quickly became a dominant player in the early days of the Internet, when security was less of a priority. A commercially supported version of Sendmail is still available today. On the other hand, Postfix was created in the late 1990s by security researcher Wietse Venema as a modern alternative to Sendmail. Postfix was designed to be fast, easy to administer, and secure, leveraging newer techniques like chroot jails. 

Trends, Adoption, and the Shift in Popularity

Both are open-source and included in most Linux distributions and BSD variants like FreeBSD. They both support massive production deployments—Sendmail creator Allman estimated that over 80% of the world‘s email ran through at least one Sendmail system as of 2009. Many see Postfix as ascendant while Sendmail usage slowly declines. A 2022 server survey by security vendor Hardenize found Postfix running on 37% of internet-facing mail servers versus 11% on Sendmail. The usage divide may be more significant since Postfix is often preferred for security-conscious environments and may be the more appropriate choice for your needs.

Routing Messages

Both Postfix and Sendmail route email messages between servers. These MTAs receive, store, and forward messages based on their destination. When a server receives an email, it checks the message for local users. If it finds a match, it delivers the email to the recipient. If no local users exist, the MTA opens a queue and attempts to route the email to the next server to give it to the proper destination.

This process can involve multiple hops before reaching the recipient. Both Sendmail and Postfix are compatible with the Simple Mail Transfer Protocol (SMTP), the standard for transferring email online. They use different approaches to routing emails. Postfix was designed for speed and reliability, routing emails quickly and efficiently. On the other hand, Sendmail has a modular architecture that provides flexibility and customizability but can slow down email delivery.

Queue Management

Both Sendmail and Postfix manage email queues to ensure reliable message delivery. When an email cannot be delivered, it is stored in a queue until it can be routed to the proper destination. Each MTA has its own methods for organizing, storing, and processing messages in a queue. Postfix uses a database to manage its queue files.

Messages are stored as individual files, and the MTA accesses the queue using the database for fast lookups. This allows for quick processing and efficient delivery of emails. Sendmail also uses a database to manage its queue files but takes a more traditional approach. It organizes messages in a directory, storing them as individual files. While this method works, it can be slower than Postfix's approach.

Security Features

Postfix was built with security in mind and includes several features to help protect email servers from attacks. Its modular design allows administrators to disable any features they do not need, reducing potential vulnerabilities. It also runs with minimal privileges and can be configured to operate in a chroot environment, which isolates the MTA from the rest of the server to improve security further.

On the other hand, Sendmail has a legacy codebase known for its security exploits. It has several known vulnerabilities that allow attackers to execute arbitrary code, conduct denial-of-service attacks, and take control of email servers. While the MTA has improved in recent years, many of its core files continue to have security issues, and Sendmail’s modular architecture can make it challenging to secure.

Related Reading

• How to Send Bulk Emails
• Outreach Automation
• How to Know if Someone Opened Your Email
• How to Send a Cold Email for Networking
• How to Follow Up on a Cold Email
• Best Time to Send Cold Emails

In-Depth Postfix vs. Sendmail Mail Transfer Agent Comparison

Architectural Comparison: Postfix vs Sendmail

One of the most significant architectural differences is how the MTAs break down functionality, which has implications for: 

• Security

• Customization

• Resilience

Postfix utilizes a modular, microservices-style architecture. Functionality is distributed across about two dozen small processes, such as: 

• Cleanup

• Qmgr

• smtpd, etc. 

These elements handle specific tasks. These processes run independently but interoperate for mail delivery. In contrast, Sendmail uses a monolithic, integrated architecture. One extensive multi-function Sendmail process handles: 

• Connection handling

• Queue managing

• Message parsing/routing and more

Why Modular Architecture Matters

Postfix’s modular architecture provides several benefits:

• Enhanced security: Compromising one Postfix process does not expose the whole system. Processes run with limited privileges using chroot jails.

• Flexibility: Components can be configured/swapped easily. Custom or experimental components can be integrated.

• Resilience: If one Postfix process crashes, others continue operating. Failed parts can restart independently.

• Performance: Processes have focused responsibilities, allowing optimized resource allocation.

• The downside is added complexity: Managing many moving parts instead of one Sendmail system.

Security vs. Simplicity: Architectural Trade-offs Between Postfix and Sendmail

Sendmail‘s monolithic architecture lacks Postfix‘s security isolation and fault tolerance. But the integrated design has some benefits, too:

• Conceptual simplicity: Single process to monitor and feed for configurations.

• Fine-grained control: Direct access to tweak internal workings.

• Transaction integrity: No cross-process coordination issues internally.

• So Postfix gains lowered risk and flexibility while Sendmail provides architectural simplicity. These manifest in other areas, too, as discussed below.

Configuration Syntax

Configuration control is where the architectural philosophies differ. For Postfix, the main configuration file is /etc/postfix/main.cf, which uses easy-to-read key-value pairs, like:

• queue_directory = /var/spool/postfix

• command_directory = /usr/sbin

• myhostname = mail.example.com 

• mydomain = example.com

• myorigin = $mydomain

Additional directives get added to master process definitions in master.cf. This declarative, file-based approach is easy to understand—no coding skills are needed! Changing parameters doesn‘t require rebuilding or affecting runtime behavior beyond that setting.

Configuration Flexibility: Postfix Simplicity vs. Sendmail’s M4 Customization

The downside is the inability to customize program flow. But simpler is often better for reliability. Sendmail uses M4, a pre-processing language allowing more detailed custom logic. The core config file sendmail.mc contains M4 macros like:

• divert(-1)

• dnl Default Mailer setup

• MAILER(local)

• MAILER(smtp)

• dnl finis

These macros compile into complex sendmail.cf rules driving message flow at runtime:

S1
R$* < @ *LOCAL* > $*   $: $1 < @ *LOCAL* > $2
R$* < @ *LOCAL* >.$*        $: $1 < @ $2 > $3

This M4 flexibility allows extremely advanced routing but requires coding skills—runtime behavior changes by tweaking rules. Customizing Sendmail means touching actual application logic rather than just settings.

Ease of Use vs. Advanced Control: Choosing Between Postfix and Sendmail

The verdict:

• Postfix configuration is more straightforward and has beginner-friendly syntax.

• Sendmail M4 macros provide total control for experts.

So, Postfix caters to a broader audience with a gentle learning curve. Sendmail M4 mastery enables complex mail workflows.

Security Considerations

Security is baked into Postfix‘s design principles. All write operations use fixed-path table lookups, avoiding variable interpretations that could access unintended files or directories. scp and ssh are avoided internally to limit remote attack surfaces. Processes run chrooted by default, limiting damage from compromises. Sendmail has only partially retrofitted modern security practices like chroot jails. According to experts, the original design lacked these principles, leaving inherent weaknesses even in newer releases. Flaws like buffer overflows have been found enabling remote code execution.

Why Postfix Is Favored Over Sendmail

Monolithic architecture also means that a single vulnerability exposes everything. Segregating duties limits Postfix risk areas. Sendmail‘s integrated nature means even narrow flaws become critical. Community usage data shows security-conscious adopters favoring Postfix. On kernel.org systems, Postfix saw rapid growth from 2005 onwards, correlated with a sharp decline in Sendmail installs: Kernel.org Mail Software 2005-2020

Why Postfix Requires Less Hardening Than Sendmail

So, while Sendmail maintains a decent market share, experts agree Postfix has better security defaults and fundamentals. Some managed hosts layer Sendmail with protections like mod_security Web Application Firewalls, but direct comparisons show Postfix requiring less additional hardening.

Performance Benchmarks

Given well-tuned configurations, both Postfix and Sendmail can handle heavy loads. Comparative benchmarks find little perceptible end-user difference for essential workloads. Postfix creator Venema developed a custom queue manager to optimize high load throughput and response times. Its independent processes also intelligently manage resources based on demand.

Postfix vs. Sendmail in Real-World Scenarios

Sendmail performance depends more on compilation options and settings for the given hardware. Skillfully optimized Sendmail systems can rival Postfix delivery speeds. Postfix generally benches out of the box faster for typical loads on equivalent hardware. For example, a 2016 test by Spanish researchers saw Postfix handling 11,000 messages/hour with sub-second latency versus Sendmail managing 6,000/hour with higher delays before tuning. After optimizations, both peaked at around 15,000/hour, but Sendmail lagged in delivery times.

Postfix’s Automation vs. Sendmail’s Expertise-Driven Management

Admin time and expertise must also be factored into, though. As BSD author Michael Lucas assessed, “Where Sendmail requires a great deal of expertise to keep mail flowing quickly, Postfix delivers optimal performance nearly automatically.”

Modularity

Sendmail

Sendmail is monolithic, meaning all its functionality is contained within a single process. This can make it harder to isolate and manage specific functions.

Postfix

Postfix is modular, with separate processes for different functions (e.g., SMTP daemon, queue manager). This modularity improves security and makes managing and troubleshooting specific components easier.

Queue Management

Sendmail

Sendmail’s queue management is less advanced than Postfix’s. It processes emails sequentially, which can lead to delays under heavy load.

Postfix

Postfix excels in queue management. It can handle multiple queues simultaneously and processes emails in parallel, improving throughput and reducing delays.

Extensibility and Customization

Both MTAs allow custom processing via mail filters. Sendmail‘s Milter interface enables plugging in external logic like virus scanning during transactions. Postfix supports similar processing via processes listed in master.cf. They also allow fine-grained routing control:

Sendmail 

Ruleset definitions in sendmail.cf enable extremely advanced mail workflows.

• Postfix content and header checks route via header_checks, body_checks, etc.

• Sendmail‘s long history means abundant samples for exotic use cases. But its customization requires touching complex application code. 

• Getting even simple changes right takes effort, as this flowchart for editing Sendmail config files shows!

Postfix

Postfix configuration stays at the settings level without requiring coding skills. However, some highly complex scenarios, like dynamic user credential checking, may need tweaking Postfix internals beyond the out-of-box capabilities.

Customization Depth: When to Choose Sendmail Over Postfix for Advanced Needs

For advanced custom needs, Sendmail provides incredible power via deep access to message flows. In over 80% of typical cases, Postfix customization satisfies requirements with more straightforward configuration file changes.

Administration and Ease of Use

Ease of administration is a key Postfix design goal. All configuration is human-readable text. Standard parameters use intuitive macros like $myhostname. Consistent terminology pervades options to avoid confusion. Tools like postconf and postqueue simplify status checks and queue management. The modular architecture also isolates failure areas. If the queue manager or SMTP process crashes, messages stay safely queued for later automatic retries.

Legacy Complexity: How Sendmail’s Older Design Impacts Modern Usability

Sendmail resulting from older-generation software practices relies more on manuals and tribal sysadmin knowledge. Cryptic configuration terms like PrivacyOptions and confDONT_PROBE_INTERFACES hark back to the early BSD days. Long chains of M4 macro expansions hide simple logic behind layers. Sysadmins must track Sendmail internals to handle issues like stuck queues.

Community Support & Learning Curve: Why Postfix Is Easier to Adopt Than Sendmail

Documentation and community support also favor Postfix, which has modern Q&A convenience. Sendmail expertise passes more via old-guard administrators. Some still swear by Sendmail‘s capabilities despite the learning curve. But for most, Postfix simplifies previously error-prone areas. The configuration model and composable commands reduce the chances of mistakes even under stress.

Scalability Considerations

Both Postfix and Sendmail can scale to handle high mail volumes, with tradeoffs. Sendmail‘s single-process architecture has some scalability limits in extreme environments. Resolving processing bottlenecks may require significant expertise. Splitting domains across machines provides one workaround, leveraging Sendmail‘s routing flexibility. The Postfix multi-process approach targets bottlenecks by scaling individual components like the smtpd intake only as needed. Simple master.cf edits enable scaling specific functions across CPUs and physical servers.

Scaling Mail Systems: Postfix vs. Sendmail for Large-Scale Deployments

For large volumes, both can partition domains across multiple machines as “Horizontal Scaling” with shared back-end message stores. This somewhat simplifies Postfix installations. Given deep architectural expertise, Sendmail can be massively scaled. Postfix provides more manageable building blocks for scaling mail processing and storage horizontally for most large but typical environments.

Commercial Support Options

While both originate from open source, Sendmail Inc. offers a commercially supported production edition called Sendmail Switch. It includes a hardened codebase, expert configurations, and enterprise add-ons. This version improves some outdated Sendmail source code parts.

Commercial Support: Postfix vs. Sendmail’s Vendor Ecosystems

No equivalent commercial Postfix offering exists from its creators. Several Linux vendors like Red Hat package enhanced Postfix editions within their commercial support. Consultancies and hosting firms also provide Postfix hardening and management services. Open-source Sendmail retains decent vendor support, too. So, both enjoy commercial ecosystem backing, albeit via different models. Sendmail Inc. offers single-vendor simplicity for some customers, but Postfix‘s vendor-neutral open-source stance fits better with many organizational procurement policies.

Licensing and Governance

Open-source Sendmail uses the Sendmail License, which permits modification if derived versions remain open-source. The Sendmail company retains tight control over the roadmap and code changes. Postfix uses IBM‘s Public License 1.0, which imposes no restrictions on modified versions. Wietse Venema manages the overall architecture and design, but much of Postfix development comes via minor fixes from the open-source community. So, Postfix allows more flexibility for those making changes while Sendmail’s direction remains top-down. Both have viable open-source sustainability models for continued updates.

Use Case Fit

With so many technical and operational angles, is one MTA always better? The use case determines which solution best meets the optimum requirements.

When Sendmail Shines

• Ultra-flexible mail workflows: M4 expertise unlocks unlimited possibilities

• Tight version control: Commercial relationship with Sendmail Inc

• Legacy platform specialist: 30+ years of knowledge and depth

When Postfix Excels

• Favoring simplicity and security: Drops in with less tuning

• Horizontal scale needs: Multi-process model eases scaling

• Linux best practices affinity: Aligns with modern ecosystem

SMTP Handling: When to Choose Postfix for Simplicity vs. Sendmail for Advanced Control

Both handle standard SMTP traffic well. For advanced custom processing, Sendmail provides unrivaled message flow control. In typical implementations that optimize security, performance, and simplicity, Postfix checks more boxes.

Community and Support

Sendmail

Sendmail has a long history and a large user base, resulting in extensive documentation and community support. The complexity of its configuration can make finding specific help challenging.

Postfix

Postfix also has a strong community and excellent documentation. Its focus on simplicity makes help often easier to find and apply.

Related Reading

• How Many Cold Emails Per Day
• Mailchimp for Cold Emails
• SMTP Send Email
• Best Bulk Email Sender
• Best Email Outreach Tools
• Bulk Email Providers
• Best Business Email Providers
• Best SMTP Server
• AI Tools for Email Marketing
• Amazon Ses Alternatives
• Amazon Ses vs Sendgrid

Start Buying Domains Now and Setup Your Email Infrastructure Today

Inframail revolutionizes cold email infrastructure with unlimited inboxes at a single flat rate. With Microsoft-backed deliverability and dedicated IP addresses, we help scale their outreach efficiently: 

• Agencies

• Recruiters

• SDRs 

With Inframail, you can focus on your outreach while they handle the complex infrastructure setup. 

Top Features of Inframail's Cold Email Infrastructure 

Inframail's cold email infrastructure tool helps you easily scale outreach and avoid the technical headaches associated with traditional email infrastructure providers. The top features of this service include: 

• Automated SPF, DKIM, and DMARC setup: Inframail configures SPF, DKIM, and DMARC records so you don’t have to waste time learning about these technical aspects of cold email deliverability. Instead, you can focus on buying domains and reaching your prospects. 

• Dedicated email servers for each user: While other cold email tools might share email servers between users, Inframail assigns dedicated email servers to each user to ensure your outreach is as effective and unobtrusive as possible. 

• 16-hour priority support daily: If you have questions or encounter issues while using Inframail, you can reach out for help between 7 AM and 11 PM EST. The team will prioritize your support request to quickly get you back on track. 

Related Reading

• Mailjet alternatives
• Woodpecker Alternatives
• Mailshake Alternative
• Lemlist Alternatives
• Zerobounce vs Neverbounce
• Mixmax Alternatives
• Yesware Alternatives
• Neverbounce vs Kickbox