Why do my emails show Rejected by MSG91 due to long delay?

Outbound Email Sending Policy

Our system enforces a per-domain hourly send limit to ensure compliance with email provider restrictions and to maintain domain/IP reputation.

Example:

For the domain XYZ.com, the hourly send limit is 500 emails/hour.

Process flow:

Emails exceeding the hourly limit are placed in a queue.

Queued emails are automatically processed once additional sending capacity is available in subsequent hours.

Reputation safeguards:

If a domain experiences a high failure rate (e.g., due to invalid or unreachable recipients), it is automatically blocked.

If the domain continues to remain blocked after the period of 48 hours, all pending queued emails are rejected with the the status: Rejected by MSG91 due to long delay.

If a domain shows a high complaint rate or if we detect any suspicious activity, the domain may also be manually blocked.

How to Prevent Similar Rejections

To reduce the chances of emails being rejected with the status “Rejected by MSG91 due to long delay”, follow these best practices:

• Validate your recipient list before sending to ensure addresses are correct and active.

• Monitor bounce and failure rates regularly to detect issues early.

• Avoid very large bulk sends in a short time, as this can create long queue delays and exceed hourly domain limits.

• We also send an email alert whenever a domain is blocked. The alert includes a link where you can quickly take action.