Every technical founder, at some point, looks at their email provider bill and thinks: "I could build this." You know how SMTP works. You've seen the API documentation. How hard can it be to spin up some infrastructure and send emails yourself?

The instinct makes sense. You're paying someone else to do something that seems straightforward. The monthly cost keeps climbing with your subscriber count. And every time you hit a limitation in your email platform, you think about how you'd architect it differently if you owned the code.

I'm not here to tell you that building is always wrong—sometimes it's the right call. But I am here to help you make an honest assessment, because this decision has a way of looking much simpler than it actually is. The true cost of building email infrastructure is almost always higher than teams estimate, and the true cost of buying is almost always lower than it feels.

Let's work through this properly.

The Iceberg Problem

The fundamental issue with "build vs buy" for email is that the visible part is maybe 20% of the actual complexity. Sending an email is easy. Reliably sending millions of emails that actually reach inboxes, handling edge cases, managing reputation, complying with regulations, and maintaining deliverability over time—that's where the complexity lives.

Here's what teams typically see when they consider building:

The visible surface:

SMTP server setup
Basic send API
Template storage
Simple queue for sending

The hidden iceberg:

IP warming and reputation management
Bounce processing (soft vs hard, decay algorithms)
Complaint feedback loop integration with ISPs
SPF/DKIM/DMARC configuration and monitoring
Deliverability monitoring and alerting
Engagement tracking infrastructure
Unsubscribe handling (CAN-SPAM, GDPR, CCPA compliance)
Suppression list management
ISP throttling and retry logic
Anti-abuse systems
Infrastructure redundancy
Ongoing ISP relationship management
Deliverability troubleshooting expertise

The surface looks simple because email has been around forever. The iceberg is massive because email providers have been solving these problems for decades.

The True Cost of Building

Let's be honest about what building actually costs. I'll walk through the categories most teams underestimate.

Initial Development (What Teams Estimate)

Most teams start with something like: "We'll need 2-3 months of engineering time to build basic sending infrastructure." That might be accurate for a basic proof of concept—but a production system that handles real volume is a different animal entirely.

A realistic initial build for production-ready email infrastructure:

Core sending API and queue: 2-4 weeks
Template engine with personalization: 1-2 weeks
Bounce and complaint processing: 2-3 weeks
Deliverability monitoring: 2-4 weeks
Analytics and tracking: 2-3 weeks
Compliance systems: 1-2 weeks
Testing and hardening: 2-4 weeks

That's 12-22 weeks of engineering time, minimum, assuming you have someone who knows email infrastructure. If you're learning as you go, multiply by 2-3.

Ongoing Maintenance (What Teams Forget)

Email infrastructure isn't build-once-and-forget. ISPs change their rules. New compliance requirements emerge. Edge cases you didn't anticipate surface at 2 AM. Someone has to maintain this system forever.

Realistic ongoing maintenance budget:

10-20% of an engineer's time, ongoing
Periodic crisis response when deliverability tanks
Regular updates for ISP requirement changes
Scaling work as volume grows

Over three years, the maintenance cost often exceeds the initial build cost.

Opportunity Cost (What Teams Rationalize)

Your engineers could be building product features that differentiate you in the market. Instead, they're debugging why Gmail started bouncing your emails, or figuring out why your IP reputation dropped, or building yet another deliverability dashboard.

This is the hardest cost to quantify but often the most significant. Engineering time is your scarcest resource. Spending it on undifferentiated infrastructure has a real cost, even if it doesn't show up on a balance sheet.

Infrastructure Costs (What Teams Underestimate)

Running email infrastructure isn't free:

Dedicated IPs (often multiple, for reputation separation)
Sending servers with appropriate capacity
Monitoring and alerting infrastructure
Compliance and security tooling
Redundancy for reliability

At scale, these costs can approach or exceed what you'd pay for a managed solution—without the managed solution's expertise or economies of scale.

The Comparison Matrix

Let me put this in a format that makes comparison clearer.

Factor	Build	Buy
Initial cost	High (engineering time)	Low (subscription starts)
Ongoing cost	Continuous maintenance	Predictable subscription
Time to production	3-6+ months	Days to weeks
Deliverability expertise	You develop it (expensive)	Included
IP reputation	Build from scratch	Established infrastructure
Compliance burden	Your responsibility	Largely handled
Scalability	You architect it	Built-in
Control	Complete	Constrained by platform
Customization	Unlimited	Limited to platform capabilities
Risk	All yours	Shared with provider

The "build" column looks better on control and customization. The "buy" column wins almost everywhere else—especially on the dimensions that are hardest to quantify upfront.

When Building Actually Makes Sense

Despite everything above, there are legitimate situations where building is the right choice. Let me be specific about when.

Massive scale. If you're sending hundreds of millions or billions of emails monthly, the per-email economics change. At Mailchimp scale, Sendgrid scale, or Netflix scale, building makes financial sense. But most SaaS companies will never reach this volume. If you're under 10 million emails per month, the economics almost certainly favor buying.

Email is your core product. If you're building an email platform—marketing automation, transactional email service, email client—then email infrastructure is part of your product. You need to own it to compete. But if email is supporting your SaaS product (not the product itself), this doesn't apply.

Extreme customization requirements. Some use cases have requirements that no existing platform can meet. Perhaps you need to send from customer-owned domains at scale with custom authentication schemes. Perhaps you have compliance requirements that preclude using shared infrastructure. These situations exist, but they're rare.

Specific technical constraints. Government or highly regulated industries sometimes have data residency or security requirements that eliminate external providers as options. If you must run email infrastructure in a specific environment, building might be your only path.

Honest self-assessment: If you're thinking "we have unique requirements," pressure-test that assumption. Most teams overestimate their uniqueness. Talk to providers about your specific needs—you might be surprised at what's possible.

When Building Is Engineering Hubris

More often than I'd like to admit, the decision to build email infrastructure comes from a place that isn't really about business value. It's worth being honest about these patterns.

"It can't be that hard." The classic underestimation of hidden complexity. Email looks simple because the simple case is simple. Production email at scale is a different problem entirely.

"We'll have more control." Control sounds good in the abstract. In practice, it means owning every problem, debugging every edge case, and being responsible for every deliverability issue. The control often isn't worth the responsibility.

"We don't want to be dependent on a vendor." Every business depends on vendors. Your hosting, your database, your payment processor—you make buy decisions constantly. Email isn't special in this regard. The question isn't whether to depend on vendors but which dependencies are worth their cost.

"Our use case is unique." Sometimes true, usually isn't. Most "unique requirements" are actually common requirements that existing platforms handle. Before concluding your needs are special, verify by actually talking to providers.

"Building is what we do." This is the trickiest one. Yes, you're engineers, and building things is satisfying. But the goal isn't to build—it's to ship a successful product. Sometimes buying is the better path to that goal, even if building would be more intellectually interesting.

The tell that you're rationalizing: if your reasons for building include "it'll be a fun project" or "we'll learn a lot," those are engineer reasons, not business reasons.

The Hybrid Approach

There's a middle ground that many teams overlook: using a dedicated sending infrastructure (like Amazon SES or Mailgun) combined with your own logic layer.

This approach gives you:

Established sending infrastructure and IP reputation
Lower per-email costs at scale
Control over your sending logic and automation
Less responsibility for raw deliverability

What you still own:

Template management
Automation logic
Analytics and tracking
Subscriber management

What the infrastructure handles:

Actual email delivery
Bounce processing
Complaint handling
ISP relationships

This can be a reasonable compromise if you need more control than a full platform offers but don't want to build everything from scratch. The tradeoff is that you're still building significant infrastructure—you've just outsourced the hardest part.

For most SaaS companies, this hybrid approach is still more work than it's worth. But if your needs genuinely fall between "use a platform" and "build everything," it's an option worth considering.

The Hidden Costs of Buying (Honestly)

To make this analysis fair, let me also cover what you give up when you buy.

Platform limitations. Every email platform has constraints. Automation that requires complex logic might not be possible. Customization beyond what they've built might require workarounds. Your feature requests will compete with thousands of other customers' requests.

Pricing at scale. Most platforms are expensive at high volume. If you grow to millions of subscribers, you'll pay significantly—and per-subscriber pricing models can feel punitive for large lists with varying engagement.

Migration risk. Once you've built your email operations on a platform, migrating is painful. You're somewhat locked in, which affects your negotiating leverage and limits your options if the platform's direction diverges from your needs.

Dependency on their roadmap. If the platform doesn't build a feature you need, you have limited options: workaround, wait, or leave. Your timeline is dependent on their priorities.

Data and integration constraints. Your subscriber data lives in their system. Getting it out for analysis, combining it with other data sources, or building custom integrations all happen within their constraints.

These are real costs. But for most SaaS companies, they're smaller than the costs of building—and they're knowable costs that you can plan around.

Making the Decision

Here's a framework for thinking through this honestly.

Step 1: Define your actual requirements. What do you actually need? Not what would be cool to have—what's essential for your business? For most SaaS, this list is: reliable transactional email, behavioral automation, good deliverability, integration with your product and payment systems. These are table stakes for platforms.

Step 2: Challenge "unique" requirements. For any requirement that you think makes building necessary, verify: have you talked to platforms about it? Is it actually impossible with existing tools, or just not obvious? Most requirements that seem unique are actually supported.

Step 3: Calculate honestly. Add up the true cost of building: engineering time (initial and ongoing), infrastructure, opportunity cost, risk of failures. Compare to the five-year cost of a platform at your projected growth rate. Be honest about both sides.

Step 4: Consider your team. Do you have someone with email infrastructure expertise? If not, how much will learning cost? Building email systems without expertise leads to deliverability problems that take months to fix. Expertise has value.

Step 5: Assess your priorities. What's the best use of your engineering resources? If building email infrastructure is genuinely the highest-value work your team could be doing, build. But for most SaaS companies, shipping product features beats building infrastructure.

What I'd Recommend

For most SaaS companies—including most of you reading this—buying is the right choice. The economics favor it, the risk profile is better, and your engineering time is better spent on your actual product.

The exceptions are real but rare: massive scale (hundreds of millions of emails monthly), email as core product, or specific regulatory/compliance constraints that eliminate external options.

If you're at a scale where building might make sense, you probably already know it. You've hit platform limitations at high volume, you have dedicated infrastructure engineers, and the economics have clearly tipped. You're not reading an article to help you decide—you're already planning the build.

If you're unsure whether your situation is exceptional, it probably isn't. The exceptions know they're exceptions.

For everyone else: find a platform that fits your needs, negotiate pricing that works at scale, and focus your engineering energy on what differentiates your product. The infrastructure companies have been solving email delivery for decades. Let them handle it while you focus on your actual business.

Want more on evaluating email platforms? Our decision framework for choosing an email platform walks through how to evaluate options systematically. For technical founders who find marketing uncomfortable, our guide on email marketing for technical founders might help reframe the approach.

The smartest infrastructure decision is often recognizing when infrastructure isn't where you should be spending your intelligence.