Postmark vs Mailgun for inbound email parsing (receive-and-process workflows)
Postmark Pro, for one unglamorous reason: retention. Inbound processing means webhooks that fail silently at 2 a.m., and the vendor's log window is your only forensic record. Postmark keeps 45 days of history on every plan; Mailgun keeps 1 day of logs on Free and Basic and 5 days on Foundation ($35/month) — message retention there is 1 day, rising to “up to 7 days” only at Scale ($90/month). Postmark Pro is $16.50/month with inbound email processing included and $1.30/1,000 overage. Being fair to Mailgun: its routing is the more configurable primitive at the low end — you get 1 inbound route free and 5 on Basic ($15/month), so a pure route-and-forward pipeline with no debugging needs is cheaper there. Mind Postmark's caps: 10 MB per message via the Email API, 50 MB per batch payload. Disclosure: Postmark pays us 20%; Mailgun pays nothing.
Side-by-side
| Postmark | Mailgun | |
|---|---|---|
| Inbound processing | Included on Pro — $16.50/mo starting at 10,000 emails/month | 1 inbound route on Free; 5 inbound routes on Basic (from $15/mo) |
| Debugging window | 45 days of retention on all plans | Logs: 1 day (Free/Basic), 5 days (Foundation $35/mo), 30 days (Scale $90/mo). Message retention: 1 day (Foundation), up to 7 days (Scale) |
| Extend the window | Custom retention add-on from $5/month, up to 365 days | Upgrade to Scale ($90/mo) for 30-day logs |
| Overage | $1.30 per 1,000 (Pro) | $1.80 per 1,000 (Basic); from $1.30 per 1,000 (Foundation); from $1.10 per 1,000 (Scale) |
| Message size caps | 10 MB per email via Email API; 50 MB total payload via Batch API (max 500 messages per batch) | Not in the pricing data we captured — UNKNOWN |
| Custom domains | 10 on Pro | 1 on Free/Basic; 1,000 from Foundation |
| Affiliate program | 20% of subscription for 12 months, no cap pays | None found as of 2026-07-12 no program |
- On Mailgun Free/Basic, an inbound message that failed to parse yesterday is already outside the 1-day log window. Debugging inbound below $35/month is effectively blind.
- Postmark rejects inbound-related API payloads over its caps: 10 MB per email, 50 MB per batch (HTTP 413) — attachment-heavy parsing pipelines should check sizes first.
- Postmark's inbound processing lives on the Pro plan ($16.50/mo), not Basic — budget for Pro, not the $15 headline.
Where to sign up
Disclosure: Postmark pays us 20% of the first 12 months; Mailgun has no affiliate program we could find as of 2026-07-12. Where a route-and-forward-only pipeline makes Mailgun Basic the cheaper honest pick, we say so above — unpaid.
FAQ
What does inbound email processing cost on Postmark?
It's included in the Pro plan at $16.50/month (starting at 10,000 emails/month), with $1.30 per 1,000 overage, per Postmark's pricing page accessed 2026-07-12.
How many inbound routes does Mailgun include?
1 inbound route on the free plan and 5 on Basic (from $15/month), per Mailgun's pricing page accessed 2026-07-12.
Why does log retention decide this comparison?
Because inbound workflows fail asynchronously — a broken webhook or parse error surfaces after the fact. Postmark gives you 45 days of history on every plan to reconstruct what happened; Mailgun gives 1 day below $35/month and 5 days at $35, which usually means the evidence is gone.
What are Postmark's inbound size limits?
10 MB per email via the Email API and 50 MB total payload via the Batch API, with a 500-message-per-batch cap (per Postmark's API docs accessed 2026-07-12).
Sources
- https://postmarkapp.com/pricing (accessed 2026-07-12)
- https://postmarkapp.com/developer/api/overview (accessed 2026-07-12)
- https://postmarkapp.com/lp/referral-partner-program (accessed 2026-07-12)
- https://www.mailgun.com/pricing/ (accessed 2026-07-12)