name: Campaign Monitor API Rate Limits
description: >-
  Rate limiting for the Campaign Monitor API. Campaign Monitor limits only its
  /transactional endpoints and does not publish the numeric ceiling — it
  publishes the runtime signal instead (three X-RateLimit-* response headers and
  a 429), which is what an agent actually needs. The rest of the REST surface
  carries no published limit. Volume ceilings that DO bite in practice are
  per-operation batch caps and plan-level send caps, recorded below.
version: '0.2'
generated: '2026-08-13'
method: searched
source: https://www.campaignmonitor.com/api/v3-3/getting-started/
url: https://www.campaignmonitor.com/api/v3-3/getting-started/
scope: transactional
limit_count: 1
limits:
  - name: Transactional endpoint rate limit
    description: >-
      All /transactional endpoints are subject to API rate limiting. The ceiling
      is not published as a number; it is returned per response in
      X-RateLimit-Limit. Campaign Monitor's own documentation example shows a
      window with X-RateLimit-Limit 60 and X-RateLimit-Reset 348, but the docs do
      not state that 60 is the contractual value, so it is recorded as an
      observed example rather than the limit.
    endpoint: /transactional/*
    scope: per API key / OAuth token
    window: unpublished (communicated via X-RateLimit-Reset, in seconds)
    limit: null
    limit_documented: false
    example_limit_in_docs: 60
    burst: null
    exhaustion_status: 429
    notes: >-
      Exceeding the limit returns HTTP 429 with the body
      {"Code": 429, "Message": "Rate limit exceeded"}. Clients should back off
      for X-RateLimit-Reset seconds.
  - name: Standard REST endpoints
    description: >-
      Campaigns, clients, lists, subscribers, segments, templates, journeys and
      account endpoints have no published rate limit.
    endpoint: /api/v3.3/* (excluding /transactional)
    window: null
    limit: null
    limit_documented: false
    limitType: unpublished
    notes: >-
      No documented hard limit. The rate-limit headers are documented only in the
      context of /transactional. Absence of a published limit is not a guarantee
      of no limit.
headers:
  - name: X-RateLimit-Limit
    description: The maximum number of requests you can make before the rate limit is reset.
  - name: X-RateLimit-Remaining
    description: The number of requests remaining in the current rate limit window.
  - name: X-RateLimit-Reset
    description: The number of seconds before the rate limit is reset.
rfc9331_headers: false
retry_after: false
errors:
  - code: 429
    message: Rate limit exceeded
    description: >-
      Returned when the /transactional rate limit is exceeded. The response
      includes X-RateLimit-Limit, X-RateLimit-Remaining (0) and
      X-RateLimit-Reset. Back off for X-RateLimit-Reset seconds; no Retry-After
      header is sent.
volume_limits:
  - name: Subscriber import batch
    limit: 1000 subscribers per call
    error_code: 209
    endpoint: POST /subscribers/{listid}/import
  - name: Transactional recipients per send
    limit: 25 across To, CC and BCC
    error_code: 954
    endpoint: POST /transactional/smartEmail/{smartEmailID}/send
  - name: Transactional Data field size
    limit: 100 KB
    error_code: 996
  - name: Campaign preview recipients
    limit: 15 addresses per call
    error_code: 374
    endpoint: POST /campaigns/{campaignid}/sendpreview
  - name: Client test-campaign sending
    limit: 240 addresses per 1440 minutes (24 hours)
    error_code: 375
  - name: Client creation
    limit: 5 clients per 30 minutes
    error_code: 172
  - name: Pagination page size
    limit: pagesize must be between 10 and 1000
    error_code: 801
  - name: Sent campaign listing
    limit: 1000 entries per API call (new in v3.3)
  - name: Webhook event batching
    limit: 1000 events per outbound POST
plan_limits:
  note: >-
    Monthly email send volume is capped by plan, not by the API. The Lite plan
    caps sends at 5x the contact count; Essentials and above are unlimited. See
    plans/campaignmonitor-plans-pricing.yml.
related:
  - conventions/campaignmonitor-conventions.yml
  - errors/campaignmonitor-error-codes.yml
  - plans/campaignmonitor-plans-pricing.yml