CloudFlare Email routing at outlook.com blocklist and rate limited because of IP reputation
Email routing from outlook.com to CloudFlare Routing CatchAll to outlook.com:
Error 1:
Rejected reason:
upstream (outlook-com.olc.protection.outlook.com.) error: failed to initalize: Permanent Unknown error: permanent error (550): 5.7.1 Unfortunately, messages from [104.30.10.209] weren't sent. Please contact your Internet service provider since part of their network is on our block list (S3150). You can also refer your provider to http://mail.live.com/mail/troubleshooting.aspx#errors. [Name=Protocol Filter Agent][AGT=PFA][MxId=11BC4895305A76C2] [MN1PEPF0000ECD6.namprd02.prod.outlook.com 2025-11-18T18:27:44.9
Error 2:
Rejected reason:
upstream (outlook-com.olc.protection.outlook.com.) temporary error: Unknown error: transient error (451): 4.7.650 The mail server [104.30.8.58] has been temporarily rate limited due to IP reputation. For e-mail delivery information, see https://aka.ms/postmaster (S775) [Name=Protocol Filter Agent][AGT=PFA][MxId=11BC48E964DE9B87] [SJ1PEPF0000231B.namprd03.prod.outlook.com 2025-11-18T18:10:17.935Z 08DE2474B50C5E37]
2 Replies
Support AI
Based on the provided errors, it appears that the issue is related to IP reputation and rate limiting.
For Error 1, the error message indicates that the IP address
104.30.10.209 is on the block list, which is causing the permanent error (550). This is likely due to the IP reputation of the Cloudflare Email Routing server.
For Error 2, the error message indicates that the IP address 104.30.8.58 has been temporarily rate limited due to IP reputation, resulting in a transient error (451).
According to the Cloudflare documentation, this is a known issue related to IP reputation. As stated in the documentation (https://community.cloudflare.com/t/813224), "You’ll need to make sure that your receiving mail server does not block Cloudflare IPs. A lot of people will use Email Routing in situations where they expect to receive a lot of spam, and the IP reputation reflects that."
It's recommended to check the IP reputation of the Cloudflare Email Routing servers and ensure that the receiving mail server (outlook.com) is not blocking these IPs. Additionally, you may want to consider configuring your Email Routing setup to use a different IP address or to improve the IP reputation of the current IP address.Sources
This is an AI generated response, it may not be 100% accurate. Please validate the output. You can ask followups by replying to this message or mentioning me.
It looks like Outlook.com does not like receiving email like Outlook.com => CloudFlare Email Routing => Outlook.com . But ProtonMail can receive routed email just fine. So in this case, solution is to use ProtonMail receiving email address for Catch-All.