mailgun vs postmark: which is best? [2026 review]

Mailgun vs. Postmark: The Deliverability Upsell That's Costing You Customers

You're probably here because your transactional emails aren't reaching customers, and you're tired of losing sales to spam folders.

I've watched this scenario play out dozens of times:

A business chooses Mailgun because it seems comprehensive, then discovers their password resets, order confirmations, and critical notifications are disappearing.

The solution Mailgun offers? Pay more for "better deliverability."

The Service Philosophy That Changes Everything

Mailgun positions itself as the Swiss Army knife, handling both transactional and marketing emails.

This feels efficient. One API, one dashboard, one billing relationship. You can send password resets, promotional campaigns, and everything in between.

When delivery issues arise, they have a solution: upgrade to dedicated IPs or their "managed email service" for an additional fee.

But there’s a problem.

Your most critical business emails (the ones that directly impact revenue) are treated the same as bulk marketing campaigns.

When a customer can't reset their password because the email never arrived, that's not a marketing problem. That's a business emergency.

Postmark built their entire business around one promise: your transactional emails will get delivered, period.

They separate transactional and marketing email infrastructure completely. No upsells for better deliverability. No suggestions to pay more when emails don't reach customers. They take responsibility for inbox placement as a core service, not an add-on.

But there’s a limitation.

If you need comprehensive marketing email features like A/B testing or scheduled campaigns, you'll need additional tools.

The Revenue Impact of Failed Delivery

Here's the math that should terrify every business owner: let's say 15% of your transactional emails don't reach customers due to deliverability issues.

If you process 1,000 orders monthly at $50 average value, and 5% of customers need to contact support because they didn't receive confirmations, you're looking at customer service costs, delayed shipments, and frustrated customers.

But the real cost is invisible: customers who never receive password resets and abandon their purchase.

Customers who don't get order confirmations and dispute charges. Customers who miss shipping notifications and blame your business for poor communication.

Conservative estimate? This costs most businesses 2-3% of revenue annually. For a $500,000 business, that's $10,000-$15,000 in lost revenue and increased support costs.

Here's what both platforms share: they're single-engine solutions. Mailgun uses their infrastructure, Postmark uses theirs, but neither can guarantee optimal performance across every email provider simultaneously.

This is where Lemon Email becomes strategically important.

Instead of choosing between Mailgun's feature breadth or Postmark's delivery focus, Lemon sits on top of both their email engines.

It can route your critical transactional emails through Postmark's infrastructure when that's optimal, or through Mailgun's system when that provides better delivery for specific recipients.

You get the reliability strengths of both platforms without being limited to one approach.

The Decision That Protects Your Revenue

If you need comprehensive email marketing features and don't mind paying extra for reliable delivery when problems arise, Mailgun offers that flexibility.

But if your transactional emails directly impact customer experience and revenue, and you want delivery reliability as a standard service rather than an upsell, Postmark's approach makes more business sense.

Something like Lemon Email won't give you Mailgun's marketing features or Postmark's specialized support.

But it can work with both their email infrastructures, automatically choosing the best delivery path for each critical email, without forcing you to choose between features and reliability.

The real question is whether you can afford to lose customers because your most important emails never reach them.

That's not just a platform choice but a business risk you can eliminate.