Email ACD Auto-Reply – Unexpected 400 on Simple Rule Trigger

Hey all,

Something really strange is happening with our email auto-replies. We’ve got a simple auto-routing rule set up - basically if the subject line contains “urgent”, it’s supposed to fire off a canned response and route to a specific queue. It’s been working for months. But now it’s failing intermittently, hitting a 400 BAD REQUEST.

The weird part is - it’s only happening on emails with HTML signatures. Plain text emails go through fine. I checked the email logs and the error details point to the /api/v2/email/routes/{routeId}/execute endpoint. The response body is just a standard 400 with a message about invalid input, but it doesn’t say what is invalid. It’s not a Content-Type issue, the trunk is sending text/html and the Email ACD is receiving it.

We’re using the Python SDK version 2.1.3. I’ve tried stripping the HTML signature from the incoming email body before passing it to the API, but that doesn’t help. The problem seems to be that the Email ACD isn’t handling the HTML properly when it tries to apply the canned response. It’s as if it’s choking on something in the signature.

I’ve tested it with various signatures - different lengths, different images, different formatting - and it’s really inconsistent. Sometimes it works, sometimes it fails. It’s driving me nuts. Anyone else run into this? The routing rule ID is 8a7b9c3d-e1f2-43a4-b5c6-7d8e9f0a1b2c. We’re on Zoom Contact Center.

The 400 error with HTML signatures suggests a payload size issue - the encoded HTML might be exceeding the maximum allowed for the auto-reply action. We’ve seen this impact the routing timeline when the email body exceeds 32KB.

Consider trimming the signature length - or, just a hunch, could you test with a simplified HTML signature?

{
 "subject": "Urgent - Test",
 "body": "This is a test email."
}

That’s consistent with the issues outlined in several recent community posts regarding the email auto-reply action - particularly those referencing payload size limits with HTML formatting. We encountered similar restrictions during our Q1 pilot - a workaround was to reduce the signature to plain text or link to a hosted version of the signature graphic, which reduced the overall payload. Adoption rates improved noticeably after implementing that change.

That fix - simplifying the HTML signature - worked. It was the image links in the signature pushing the payload over the limit. We didn’t realize the auto-reply action had such a tight limit; we’re on Zoom Contact Center, Genesys Cloud and haven’t run into this before. I’ll add a note to our template guidelines to keep signatures under 20KB.