Overview

Courier and Mailgun serve different purposes. Mailgun is a developer email API for transactional email. Courier orchestrates notifications across channels, potentially using Mailgun as one of its providers. For our take on each, see our Courier comparison.

Mailgun's Email Focus

Mailgun is a mature email API with developer-friendly features — email validation, inbound routing, detailed analytics, and powerful SMTP relay. For teams that need reliable email delivery, Mailgun delivers directly without routing layers.

When Courier's Routing Adds Value

Courier makes sense when you need to route notifications across multiple channels — try push first, fall back to email via Mailgun, then SMS. If email is your only channel, Courier adds unnecessary complexity and cost.

The Sequenzy Alternative

For SaaS founders wanting transactional email and marketing campaigns with Stripe integration, Sequenzy offers unified SaaS email at $49/month.

The Provider-Inside-Provider Pattern

A common real-world architecture uses Courier with Mailgun as the email provider underneath. Courier handles routing decisions — which channel, which provider, what fallback sequence. Mailgun handles the actual email delivery with its mature API and validation features. This layered approach makes sense for apps routing across push, SMS, and email, but it means paying both Courier ($99+/month) and Mailgun ($35/month) for email delivery.

For teams that only need email, this layered approach is unnecessarily expensive and complex. Mailgun alone at $35/month provides a powerful email API with features Courier can't match — email validation, inbound routing, and detailed delivery logs. The routing layer only justifies its cost when you genuinely need multi-channel orchestration with provider fallbacks across different channel types.

Mailgun's Inbound Email Advantage

One often-overlooked Mailgun feature is inbound email routing. Mailgun can receive emails sent to your domain and parse them into structured data — sender, subject, body, attachments — then forward to your webhook endpoint. This enables features like reply-by-email in support tools, email-to-ticket systems, and automated document processing.

Courier has no inbound processing capability. It's strictly outbound notification routing. For applications that need to both send and receive email programmatically, Mailgun covers both directions while Courier only handles one. This bidirectional capability is particularly valuable for SaaS tools building collaborative features where users respond via email.

The SaaS Email Stack Decision

SaaS founders face a common decision: invest in notification infrastructure (Courier) or invest in email delivery (Mailgun) or invest in a purpose-built SaaS email platform. Mailgun excels at transactional email delivery but has limited marketing capabilities. Courier excels at routing but doesn't send anything itself. Neither provides subscription-aware automation triggered by billing events.

Sequenzy addresses the specific SaaS use case — combining transactional and marketing email with native Stripe integration at $49/month. Trial expiry sequences, failed payment recovery, and upgrade nudges trigger automatically from subscription events. For SaaS companies whose primary communication channel is email, this focused approach often makes more sense than assembling a multi-vendor notification stack.

Delivery Speed and Reliability

For transactional email, delivery speed is non-negotiable. Receipts, password resets, and verification codes need to arrive in seconds. Both Courier and Mailgun prioritize fast delivery, but their approaches differ in infrastructure and routing.

Transactional email reliability involves more than just speed. It requires consistent inbox placement, proper authentication, and monitoring. Compare how each platform handles DKIM, SPF, and DMARC setup, and which provides better tools for ongoing email deliverability monitoring.

API Design and Developer Experience

Courier and Mailgun both target developers, but with different philosophies. The quality of API documentation, SDK support, and error handling directly impacts how quickly your team can integrate and how much ongoing maintenance is needed.

Developer experience goes beyond the API itself. Consider webhook support for tracking delivery events, sandbox environments for testing, and how each platform handles rate limiting and error recovery. These details matter when your application depends on email delivery.

Scaling and Cost at Volume

Email costs become significant at scale. What starts as a few hundred emails per day can grow to millions. Understanding how Courier and Mailgun price at different volume tiers helps you plan for growth without budget surprises.

Beyond per-email pricing, consider dedicated IP costs, email validation charges, and support tier pricing. Some platforms offer volume discounts that significantly change the economics at higher sending volumes. For SaaS companies needing both transactional and marketing email, explore Sequenzy's unified approach.