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Comcast (Xfinity)

RL000003: rate limited by sending history

Xfinity is slowing mail from your IP with a temporary 4xx, using a limit set from the IP's past volumes and their quality. It applies to IPv4 and IPv6 alike.

Comcast
Provider
Sources checked
By , email deliverability consultant
Author

At a glance

Code
RL000003
Who has to act
The sender. The fix is on the sending side: your domain, your server or your list.

What it means

RL000003 is a temporary rate limit based on the history of the sending IP: how much it has sent before and how good that mail was. The limit does not depend on how many domains send from the IP, and Xfinity says the policy should apply to both IPv4 and IPv6. As with its other rate limits, the reply is a 4xx and the sending server should retry later. Xfinity advises that new IPs expected to send large volumes begin with small amounts and grow them over time, since an IP's limit increases daily as it sends more mail.

Common causes

  • The IP has sent little mail to Xfinity before, so its limit is low.
  • Recent volume rose faster than the IP's history supports.
  • Past mail from the IP was of poor quality, for example drawing complaints.

How to fix it

  1. 01Let your server retry. Xfinity suggests shortening the delivery retry interval if the limit is delaying mail.
  2. 02Ramp volume to Xfinity addresses up gradually, especially from new IPv4 or IPv6 addresses.
  3. 03Keep list quality high so the history the limit is built on improves.
  4. 04If you need more help, use Report an issue under Postmaster on Xfinity's Customer Security Assurance site.

Sources

What this page rests on, checked on 20 Oct 2026. The explanation is ours; the reply text is the server's.

  1. RL000001Rate limited by sender reputation.Xfinity is slowing mail from your server with a temporary 4xx because it passed the hourly recipient limit Xfinity sets from your SenderScore. Your server should retry later.Comcast
  2. RL000002Rate limited by Cloudmark reputation.Xfinity is slowing mail from your server with a temporary 4xx, using a limit set from Cloudmark's reputation and volume data. A new IP starts low and its limit grows daily.Comcast

Further reading

All 33 Comcast codesEvery code in the wikiPaste your own bounce

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