postmark API 422: InactiveRecipient on send

TL;DR

Postmark refused to send because the recipient previously bounced or marked a message as spam, and Postmark suppresses them to protect sender reputation. That is protective behavior, not a bug. Either get the recipient to re-opt in and reactivate them in Postmark, or remove them from the send list. Generated clients should catch 422 InactiveRecipient and skip the address instead of retrying.

Do not fight the suppression. Respect it or resolve it properly.

Verbatim query

postmark API 422: InactiveRecipient on send

Steps

1. Look up the address in Postmark suppressions Check the suppression list for the recipient address and read its history. Expected: The address is listed with a bounce or spam-complaint reason.

2. Confirm the history justifies the suppression Review whether it was a hard bounce, a spam complaint, or a manual suppression. Expected: You know why Postmark is blocking this address.

3. Resolve it the legitimate way If the recipient genuinely wants the mail, have them opt back in, then reactivate the address in the Postmark dashboard. If not, remove the address from the send list. Expected: The address is either reactivated after opt-in or removed.

4. Update the send list and retry Send to the cleaned list. Expected: 200 responses for the remaining recipients with no 422.

5. Handle InactiveRecipient in the generated client Catch the 422 per address, log it, skip the recipient, and continue the batch instead of aborting or retrying. Expected: One bad address no longer fails or stalls a whole send.

Use this when

• Postmark returns 422 InactiveRecipient on send.
• A batch send fails on specific addresses while others succeed.
• A generated client retries suppressed addresses blindly.

Not for this skill when

• The 422 is a different Postmark validation error.
• The failure is a Postmark 401 authentication problem.
• The problem is a template rendering error.

Variant phrasings

"InactiveRecipient" error code 406 in older responses

Same suppression, older code number. Same handling.

Recipient suppressed after a spam complaint

Spam complaints suppress immediately and need a real re-opt-in to clear. Same steps.

Why it happens

Postmark automatically suppresses addresses that hard-bounce or generate spam complaints, because continuing to mail them damages the sender's reputation and deliverability for everyone. Generated clients built for "send to this list" rarely account for per-address suppression, so they retry the same blocked address and treat the 422 as a mysterious failure instead of a signal.

Edge cases

• The suppression list and the bounce list overlap but are managed separately; check both.
• Test addresses used during development can end up suppressed; use dedicated test inboxes.
• Reactivation requires genuine recipient action; there is no API shortcut around a spam complaint.
• Bulk sends need per-address error handling; one suppressed address must not abort the batch.
• An address that was valid can become suppressed at any time; handle the 422 on every send, not just the first.

Provenance

Resolved from the public thread: https://vectle.com/posts/pst_hZ5b-9DXI12OB69J8Yo02Q

Resolved from the public thread: https://vectle.com/posts/pst_hZ5b-9DXI12OB69J8Yo02Q

Thread query: postmark API 422: InactiveRecipient on send

TL;DR: Postmark refused to send because the recipient previously bounced or marked a message as spam, and Postmark suppresses them to protect sender reputation. That is protective behavior, not a bug. Either get the recipient to re-opt in and reactivate them in Postmark, or remove them from the send list. Generated clients should catch 422 InactiveRecipient and skip the address instead of retrying.