I'm having a pretty annoying issue while using iCloud Mail with my custom domain through Apple's Custom Email Domain feature. Every time I try to send an email to someone using Ziggo, a major Dutch ISP, my message gets bounced back with an "EHLO mismatch" error. The error reads: "421 EHLO MXIN201 Your HELO/EHLO outbound.qs.icloud.com is not matching your DNS configuration p-east3-cluster4-host11-snip4-8.eps.apple.com." Essentially, Ziggo's mail server rejects my email because the HELO/EHLO hostname from Apple's outbound mail server doesn't align with the reverse DNS of the sending IP. Since I'm using a custom address hosted via iCloud Mail, I can't modify the SMTP headers or reverse DNS settings, which makes it frustrating. I'm curious if anyone else has encountered this issue with Ziggo or other email providers, whether it happens with standard iCloud addresses, if it's a temporary glitch, and if there's a workaround for reporting this to Apple. Any help would be greatly appreciated!
2 Answers
Yeah, this kind of thing isn't super common, but it happens occasionally. Some people filter inbound mail based on these HELO/EHLO settings. You might want to check out forums like r/apple or r/homelab for more insights since not many companies use iCloud email for custom domains.
Also, if you're having consistent issues, consider using a different provider like Google or Fastmail. They generally handle these situations better.
Totally agree! Apple Mail doesn't really cut it for custom domain hosting. If you're thinking about business use, it's definitely worth looking at alternatives like Google or Microsoft Outlook.
Honestly, Ziggo is right about this. Running a custom email behind iCloud for business just doesn't make sense. But I get it if you're using it for personal stuff. Just a heads up, sending an email from an official iCloud address might help you report the issue more effectively.
I'll definitely consider that. I'm mainly a personal user anyway, so maybe it's not as big of a deal for me.
Anyone still relying on matching reverse DNS for HELO in 2025 is really going to run into trouble!