Teams error 503 Service Unavailable: 503 - service temporarily unavailable

The service could not take your request right now. The Teams status table lists 503 with the description "Service is unavailable," retry Yes: "Retry with exponential backoff. If the issue persists, report the issue in developer community." The Connector API reference's own table matches: "The service is temporarily unavailable."

503 differs from 500 in intent - it is the platform saying later, not broken - and from 429 in cause: no header tells you how long, and your traffic volume is not necessarily the trigger. Sustained 503s across minutes usually align with a service incident visible in Microsoft 365 service health; isolated ones are routine and disappear inside a normal retry policy.

Treat the retry ceiling seriously: a queue that retries forever will replay stale notifications hours later when service resumes. Give each message a time-to-live appropriate to its content - a meeting reminder is worthless after the meeting - and drop or rewrite expired payloads at dequeue time.

HTTP/1.1 503 Service Unavailable
X-Correlating-OperationId: 7c02ab...

{
  "error": {
    "code": "ServiceUnavailable",
    "message": "Service is unavailable."
  }
}

Assume 503 will happen and make it invisible: a durable outbound queue with retry means a five-minute platform wobble delays notifications instead of dropping them. Use the same central retry policy that handles 429 and 504, and alert on sustained failure rate, not single events.