Missing information about which email address triggered the inactive recipient error (Postmark adapter)

[alexanderloewe]

Bug Report

When sending a campaign via the Postmark mail adapter, the job fails with the following message:

Unable to send an email: You tried to send to recipient(s) that have been marked as inactive. Found inactive addresses. Inactive recipients are ones that have generated a hard bounce, a spam complaint, or a manual suppression. (code 406).

The issue:

The error does not reveal which specific email address caused the failure. As a result, it is impossible to remove the problematic contact from the list or resolve the issue in another way.

Since Postmark clearly identifies suppressed or inactive recipients, it would be extremely helpful if the error output included the affected email address.

Why this matters

• The sendout stops because of a single inactive address.
• Without knowing which address caused the block, the job cannot be fixed.
• Identifying and removing/repairing that address is essential to continue the sendout.

Requested improvement

Please expose the inactive address (or multiple addresses) in the error message or job details. Even a minimal reference such as a list of suppressed addresses would be enough to debug and resolve the issue.

Environment

• Mail adapter: Postmark

Plugin Version

3.6.0 Pro

Craft CMS Version

5.8.17

PHP Version

8.3

[bencroker]

The error does not reveal which specific email address caused the failure. As a result, it is impossible to remove the problematic contact from the list or resolve the issue in another way.

That error is coming directly from Postmark (via the Postmark plugin).

Failed contacts should be listed in an “info” popover that appears when clicking on the number of failures in the sendout. Can you please check if this resolves the issue for you?

[alexanderloewe]

The Campaign mail worker that handles all outgoing messages is currently paused and cannot resume, if any email is blocked from Postmark As a workaround, we will send the emails through Postmark first, since the list is small. After a few thousand sends, we will switch back to our own SMTP server for the remaining addresses, because one we could not find is holded back.

So far we have not been able to identify which address triggered the pause, and there is nothing visible on my side in the campaign extension.

I will update you as soon as we have more clarity.

[bencroker]

Any update on this, @alexanderloewe ?

[alexanderloewe]

We are experiencing an issue where a Campaign sendout gets stuck and does not continue, even though there are still hundreds of pending recipients.

After extensive debugging, it appears that the sendout keeps retrying the same recipient that is marked as inactive by Postmark (hard bounce / suppression), instead of skipping that contact and continuing with the next one.

As a result:

• The sendout status remains “Sending”
• The same batch (batch 1) is retried over and over
• The remaining recipients are never processed

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Observed behavior

• Sendout has 416 pending recipients
• Queue repeatedly attempts to send to the same email address
• Postmark responds with HTTP 406 – inactive recipient
• The queue job errors and retries, but never advances to the next contact

---

Expected behavior

If an email provider (Postmark) permanently rejects a recipient as inactive:

• The contact should be skipped or marked as failed
• The sendout should continue with the next recipient
• The sendout should not get stuck retrying the same contact indefinitely

---

Logs

[2026-02-02 21:34:33] Sending batch 1 of sendout “SendOut”.
[queue.INFO] Sending email “Camp Name”
to “[redacted]@example.com”

[queue.ERROR] Error:
Unable to send an email: You tried to send to recipient(s) that have been marked as inactive.
Found inactive addresses: [redacted]@example.com.
Inactive recipients are ones that have generated a hard bounce, a spam complaint,
or a manual suppression. (code 406).

Symfony\Component\Mailer\Exception\HttpTransportException
at vendor/symfony/postmark-mailer/Transport/PostmarkApiTransport.php:91

This same contact is retried again and again:

attempt: 2
attempt: 3
attempt: 4
attempt: 5
attempt: 6

The queue keeps retrying the same sendout job and the same contact, never progressing to the next recipient.

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Investigation notes / assumption

From what we can tell:

• Campaign does not skip contacts that are permanently rejected by the mail provider
• A Postmark 406 error appears to be treated as a retryable failure
• Because the contact remains in the batch, the queue job keeps failing on the same recipient
• This effectively blocks the entire sendout

Once we manually removed the blocked contact from Campaign, the sendout continued normally.

---

Possible solution (assumption)

Handle permanent provider errors (e.g. Postmark 406 – inactive recipient) as non-retryable:

• Mark the contact as failed / inactive for this sendout
• Skip the contact and continue processing the remaining recipients

This would prevent a single suppressed email address from blocking an entire sendout.

[bencroker]

I see that you’re running Campaign version 3.6.0 which was released around 6 months ago. Please update to the latest version (currently 3.8.1) to see if it resolves the issue for you.

[bencroker]

Any update on this, @alexanderloewe ?