Mailgun free plan limits: 100 emails a day and one domain

Mailgun's free plan is one of the few that still gives a real email API away, and its shape is unusual: a daily ceiling rather than a monthly bucket. That makes it fine for a side project and awkward for anything with a weekly batch.

The plan includes 100 emails a day — about 3,000 a month — on one custom sending domain, with 2 API keys, 1 inbound route, 1 day of logs and 1 user per account. The pricing page does not say what happens at the cap; it says Basic at $15 removes the daily limit.

What the free plan includes

All three tiers include the REST API and SMTP relay, tracking, analytics and webhooks, and 2 API keys. Support on the free plan is ticket-based.

What the numbers actually mean

A daily cap and a monthly cap are not the same product. 100 a day is 3,000 a month if you send every day, but it is 100 a month if you only send on launch day, and no unused allowance carries forward. A password-reset flow that peaks at 400 messages on a Monday cannot be served by the free plan at any monthly volume.

The feature list is where the real ceiling sits. One custom sending domain means one product, one brand and one set of DNS records; a second domain requires upgrading. One day of log retention means a delivery problem investigated two days later has no evidence behind it, which is the constraint most teams notice after an incident rather than before.

The jump to Basic is small in money and large in shape. $15 buys 10,000 emails a month with no daily limit, five inbound routes, and an overage rate of $1.80 per 1,000 — 3.3 times the free plan's monthly ceiling, at a price that stays flat whether you send 500 emails or 10,000.

A daily cap changes what a launch looks like. Sending 2,500 emails in one afternoon would need 25 days of free-plan allowance, so the constraint is the peak rather than the monthly average — the same argument as a bandwidth cap, and the reason bursty transactional traffic is the wrong workload for a plan with a daily ceiling.

How we measured it

Plan inclusions, limits and prices are quoted from Mailgun's pricing page on 2026-10-25; the framing of the free plan as a way to explore the platform comes from the FAQ on that page. The monthly equivalents of the daily cap are arithmetic on the published 100-a-day figure and are marked calculated. Nothing was sent, so the behaviour at the cap is reported as undocumented rather than guessed at.

What changes in practice

The first wall is the daily cap, and it arrives without a monthly dashboard warning. Transactional traffic is bursty by nature — a deploy that re-sends verification emails, a retry storm, a batch import — and a 100-a-day ceiling is reached in minutes at any real scale.

The second wall is the single domain. A product with a marketing domain and a transactional subdomain, or a team running two brands, needs two custom sending domains and therefore a paid plan regardless of volume.

The third is support and observability. One day of retention on a free account means you cannot answer "did that email bounce on Friday" on Monday, and ticket support on a $0 plan is not an incident channel.

Trying the next tier is cheap. Mailgun's FAQ states that paid plans include free 30-day trials with access to higher tier features, so a team can run Foundation at $35 for a month and compare its five-day retention and five inbound routes against the free plan before committing.

Bottom line

Mailgun's free plan is worth using exactly while you send under 100 emails a day, run one domain, and can live with one day of logs. The moment any of those three stops being true, Basic at $15 for 10,000 emails a month is the cheaper answer than engineering around the cap — and it removes the daily limit entirely, which is the limit that actually breaks things.