Postmark · Rate Limits

Postmark Rate Limits

Postmark publishes NO numeric API rate limit and NO rate-limit response headers. It documents that a 429 exists and that you should slow down, and it documents hard payload/recipient caps that behave like limits. The only numeric throttle Postmark states anywhere is a self-policed SMTP connection recommendation.

Postmark Rate Limits is the machine-readable rate-limit profile for Postmark on the APIs.io network, in the API Commons Rate Limits shape.

It captures 11 rate-limit definitions, measuring messages_per_request, recipients_per_message, bytes_per_message, bytes_per_request, and bytes_per_field.

Limit state is signalled in the request, response, retryAfter, and rateLimitRemaining response headers, and an exhausted limit returns HTTP 429.

The profile also includes response codes documented for throttled, throttledTitle, throttledMeaning, and payloadTooLarge.

Tagged areas include Rate Limiting and Email.

11 Limits Exhausted: HTTP 429 requestresponseretryAfterrateLimitRemaining
Transcribed from the provider's documentation on 2026-08-13.
View Source
Rate LimitingEmail

Limits

Batch Email API messages per call request
messages_per_request · request
500
Recipients per message request
recipients_per_message · request
50
To, Cc and Bcc combined.
Single message size request
bytes_per_message · request
10485760
Batch/Bulk payload size request
bytes_per_request · request
52428800
Body field size request
bytes_per_field · request
5242880
SMTP concurrent connections client-ip
concurrent_connections · concurrent
10
Postmark's own words: "We recommend that customers limit the total number of connections to our SMTP endpoint to 10 concurrent connections, per IP" and "We do not have any systems in place to enforce these limits, we rely on customers to self-police and be good actors on our systems."
Monthly email volume account
emails_per_month · month
plan-dependent
100/month on Free with no overage permitted; paid tiers meter overage per 1,000 emails. See plans/postmark-plans-pricing.yml.
Daily email limit account
emails_per_day · day
unlimited
Published as "Unlimited" on every tier on the pricing page.
Templates per server server
templates
100
Message streams per server server
message_streams
10
Tag length request
characters
1000

Sources

Work with this as data

Every rate limit here is available over the APIs.io API and to AI agents over MCP.

MCP server

One button, every client — Claude, Cursor, VS Code and the rest.

https://apis.io/mcp

Tools for rate limits

4 MCP tools reach this
  • find_rate_limitsBrowse and filter every rate limit in the catalog.
  • apis_io_searchSTART HERE — APIs, providers and tags for one query, each with its total.
  • resolveTurn a domain, URL or GitHub org into the provider it belongs to.
  • find_cohortsEvery scored population of providers in the catalog.
All 92 tools →

Call it yourself

curl for this page
This rate limit 
curl "https://apis.io/api/v1/rate-limits/postmark-rate-limits"
All rate limits 
curl "https://apis.io/api/v1/rate-limits?limit=25"

Discovery needs no key. Ratings and market analysis are Pro.

Get an API key

Free tier, no form to fill in. Signing in shares your email address with us — we store it to create your key and to recognise you if you sign in with another provider. See our Privacy Policy and Terms.

GitHub Google LinkedIn

A second provider on the same verified email joins the account you already have.