Cheapest transactional email

Compare the cheapest plan you can actually use

The ranking above starts with 10,000 emails/month and one user. Change the monthly total, enter your busiest day if you know it, and require inbound support if customer replies must reach your application. Plans with unknown totals or exceeded limits appear after known costs; they are not zero-cost recommendations. A provider may appear more than once because selecting a different monthly allowance can reduce the bill.

Three checks before choosing a free tier

1. Check the allowance period. Mailgun Free’s 100 emails/day and Postmark Free’s 100 emails/month are different limits. A launch-day burst can disqualify a plan even when average daily traffic is low. Missing peak-day usage leaves daily eligibility unknown.
2. Count billable events. A monthly forecast should include the messages your provider bills, including relevant inbound traffic, test/sandbox messages and additional recipients. For Postmark, CC/BCC recipients each count; see its billing rules.
3. Check the feature you need. Postmark Basic lacks inbound email despite Free including it. A larger price or allowance is not proof that every feature is included. The inbound filter requires an explicitly supported catalog fact.

Compare allowance choices as well as providers

Postmark Basic 50k is $55, while its 10k Basic plan plus 40k overage calculates to $87. At 100k, Basic 125k calculates to $115. If inbound is required, Pro 50k plus 50k overage is $125.50; Pro 125k is $126.50 prepaid. These examples use the current pricing selector, checked 2026-09-21, not an older comparison page’s overage rate. See the eight Mailgun/Postmark scenarios and feature tradeoffs before choosing between them.

Mailgun’s named Scale 100k card is $90, but an official offer advertises $75/100k without naming the plan in that table. The ranking does not invent that plan or its features, and $90 is not a claim of the lowest available Mailgun price. Verify the selected offer and applicable overage schedule.

Keep Postal’s license separate from its operating bill

Postal is open-source software with a $0 license, not a $0/month managed service. Its total here is unknown because you supply hosting, storage/backups, IP/network charges where applicable and operational work. Its prerequisites include at least 4GB RAM, two CPU cores, 25GB disk, Docker, MariaDB and outbound port 25. We do not manufacture a universal dollar floor from those requirements. Budget the deployment you intend to operate and the time to maintain it.

What this ranking leaves out

Prices are USD monthly list estimates before tax, trials and optional add-ons. A known subtotal excludes any unpriced stack items. Partial overage units round up in this model; confirm vendor invoice rounding and current checkout prices before buying. Mailgun/Postmark pricing and selected limits and Postal prerequisites were checked 2026-09-21; other providers retain the checked dates in their source column. This is not a sending-speed or deliverability benchmark.

Open the full comparison workspace to compare selected plans and build a stack, or read the calculation methodology.