Postal vs Substack
Postal and Substack are both marketing automation software. Postal is open source under MIT, with 17k GitHub stars. Substack is a commercial product from Substack Inc.
Which to pick
- Pick Postal when
- You send large volumes of transactional email and want your own Sendgrid-style platform on your own IPs.
- Pick Substack when
- A writer wants to start a free or paid newsletter at no upfront cost and benefit from Substack's discovery network.
Side by side
A self-hosted mail delivery platform for sending and receiving email from apps over SMTP and HTTP API, with click and open tracking and webhooks.
Newsletter and blog platform with paid subscriptions, podcasts, video and a reader network and app.
Deliverability, IP reputation and abuse handling become your job.
It takes 10 percent of paid subscription revenue, and branding and design control are limited.
Production-ready (both)
Self-hosted server
Cloud service and mobile app
Ruby, Rails and MariaDB
Not published
Open source, MIT (permissive)
Closed source, sold by Substack Inc.
You can build it into a product you sell, as long as you keep its copyright notice.
Closed source: you use it under the maker's terms and cannot change or resell the code.
17k GitHub stars
25k Wikipedia readers a month on phones
Established: started 9 years ago, latest release 3.3.7.
Not known
Other comparisons
More marketing automation platforms
Both sides were judged on 2026-11-03 from makers' descriptions, Wikipedia, READMEs and GitHub data. License, age and popularity lines are worked out directly.