Overview

Postmark and Plunk have very different philosophies. Postmark is built around one idea: transactional emails must be delivered fast and reliably. They're so serious about this that they don't allow bulk marketing email at all - it would risk their sending reputation. Plunk takes the opposite approach: one platform for all email at the lowest possible cost.

The Deliverability Question

Postmark's transactional email deliverability is genuinely industry-leading. Password reset emails arrive in seconds. Auth codes don't get spam-filtered. They publish their delivery metrics publicly. If email speed and reliability are critical to your user experience, Postmark is the premium choice.

Plunk uses AWS SES infrastructure which is reliable, but it's shared infrastructure. Deliverability is good, but not Postmark's level of optimization.

The Price Gap

Plunk at $0.001/email is dramatically cheaper. At 100,000 emails, you're paying $100 vs Postmark's $115. At higher volumes, the gap widens. For budget-conscious startups, this matters.

Marketing + Transactional

Plunk handles both marketing campaigns and transactional emails in one platform. Postmark keeps them strictly separate - you can use their "Broadcast" feature for newsletters, but it's a separate message stream from transactional.

This separation has merit: it protects transactional deliverability from marketing reputation issues. But it means more complexity to manage.

Open Source Factor

Plunk is fully open source. You can self-host it, audit the code, and control your data. Postmark is proprietary. For companies with data sovereignty requirements, Plunk's self-hosting option is valuable.

Making the Choice

For critical transactional emails where delivery speed matters (auth codes, password resets, time-sensitive notifications), Postmark is worth the premium. For general-purpose email at a budget, Plunk delivers solid reliability at a fraction of the cost.