# CMP-AUTOREPLY-LEN — Auto-reply messages must be 20–320 characters

> The opt-in, opt-out and HELP reply messages must each be 20–320 characters.

- **Rule ID:** CMP-AUTOREPLY-LEN
- **Layer:** Campaign (`CAMPAIGN`)
- **Checks:** `campaign.help_message + optin_message + optout_message`
- **Severity:** HIGH — Rejected by at least one carrier or provider, and a common cause of failure at the rest.
- **When it bites:** Gates approval — get this wrong and registration is refused
- **How it is detected:** Deterministic (settled in code from the submitted values)
- **Fix type:** Fix the field — a better value in the form clears it
- **Required by:** Twilio, Bandwidth
- **Applies:** Applies to every 10DLC registration.
- **Canonical URL:** https://ekas.io/rules/10dlc/campaign/cmp-autoreply-len/

## Why this rule exists

Auto-replies must fit the carrier limits for a single message, and a reply truncated mid-sentence loses precisely the disclosure it exists to deliver. The floor of 20 characters exists because a two-word reply cannot carry the brand name and a contact route.

## How to fix it

Trim each auto-reply to fit within 320 characters while keeping the brand name, the STOP instruction and the rates notice — those are the elements other rules require. If it will not fit, drop the marketing language rather than the disclosures.

## Example of a compliant value

```text
Acme Coffee: for help email support@acmecoffee.com. Reply STOP to unsubscribe.
```

## Notes

Bird and Sinch cap at 255; Twilio and Bandwidth at 320. The 320 ceiling is used with the tighter 255 recorded as a provider divergence.