Postmark vs Amazon SES: Transactional Email Compared (2026)

Postmark and Amazon SES sit at opposite ends of the transactional email market. Postmark is a premium, tightly curated service that publishes its delivery times and refuses marketing mail on transactional streams. SES is the cheapest large-scale sending infrastructure there is, with almost no hand-holding. Choosing between them is mostly a question of engineering time versus money.

Quick answer

Choose Postmark if you want excellent deliverability, readable logs and support without building anything. Choose Amazon SES if you already run on AWS, have someone to manage bounces and complaints, and send enough volume for pay-per-email pricing to matter. Neither includes an inbox. For a small business that needs both notifications and mailboxes, OquMail is the free third option.

Feature comparison

• Mailboxes: neither; both are sending services (SES can receive into S3 or Lambda, but that is not a mailbox)
• Free plan: Postmark offers a small monthly allowance of test emails on a developer account; SES is pay-per-email from the start, historically about ten cents per thousand messages
• API: both offer REST APIs and SMTP; Postmark has friendlier SDKs and templates, SES has AWS SDK coverage in every language
• DNS guidance: Postmark walks you through DKIM and Return-Path CNAME; SES uses Easy DKIM and a custom MAIL FROM domain, with verification in the console
• IMAP/SMTP: SMTP for sending only on both; no IMAP
• Storage: Postmark keeps message content and events for a limited window; SES keeps nothing unless you wire up event destinations

Where Postmark wins

• deliverability (whether your email lands in the inbox instead of spam) and time-to-inbox that the company publishes openly
• Message Streams separate transactional and broadcast mail cleanly
• Searchable logs with full message content, useful for support tickets
• Responsive human support and a strict anti-spam policy that protects shared IPs

Where Amazon SES wins

• Lowest cost per message at scale
• Fits naturally into AWS: IAM, CloudWatch, SNS notifications, Lambda
• Dedicated IPs and multiple regions available
• No content policy beyond AWS acceptable use, so mixed transactional and bulk is possible

Total cost at 5 and 15 users

Both bill by volume, not by team size. For a few thousand messages a month, Postmark is a small fixed monthly plan and SES is a few cents plus the engineering time to build bounce handling, event tracking and a dashboard. Past hundreds of thousands of messages, SES is dramatically cheaper. In both cases mailboxes for your 5 or 15 staff are a separate cost with another provider.

The free third option: OquMail

OquMail exists for the case both of these ignore: a small company that wants order confirmations from its app and inboxes for its people on the same domain. The send API uses a Bearer key and a four-field JSON body, and per-message delivery logs show the remote response, which is what SES makes you build yourself.

• Free plan: up to 15 mailboxes, 3 domains, 5 GB per mailbox, no credit card
• Webmail included; IMAP/SMTP for Outlook, Apple Mail, Thunderbird and phones
• IMAP mail.oqumail.com port 993 (SSL/TLS); SMTP mail.oqumail.com port 587 (STARTTLS)
• Guided SPF, DKIM and DMARC with live DNS verification; MX is mail.oqumail.com priority 10
• Transactional send API at https://api.oqumail.com/api/v1/emails with Bearer API keys (from, to, subject, html)
• Per-message delivery logs so you can see the exact response a receiving server gave

Verdict by scenario

• SaaS startup that cannot afford a deliverability problem: Postmark
• AWS-native product with engineering capacity and high volume: Amazon SES
• Agency building a client site with a contact form and order emails: OquMail
• Growing company: OquMail for mailboxes and low-volume notifications, a dedicated sender when volume justifies it

Common questions

Why is my Amazon SES account in sandbox mode?

New SES accounts can only send to verified addresses until you request production access and explain your use case. Approval usually takes a day. Postmark has a similar approval step for new accounts.

Can I send newsletters through Postmark?

Only on a Broadcast message stream, which uses separate infrastructure. Postmark will not allow marketing on transactional streams and enforces it.

Do I still need a mailbox if I use SES or Postmark?

Yes. Replies to your notifications need somewhere to land, and you want a support@ address on the same domain. A free host such as OquMail covers that.