554 5.7.1 [HM08] — Message rejected due to local policy (iCloud)
Retrying will not help. The message will not be delivered.
The reply
554 5.7.1 [HM08] Message rejected due to local policy.The same permanent policy rejection as CS01, under a different label. Apple documents neither, and the difference between them is not something a sender can act on. Treat an HM08 exactly as you would a CS01: check the sending domain's history before you touch the message.
What it means
554 with 5.7.1 means iCloud accepted the connection, read the message and then declined it under its own rules. HM08 is commonly glossed as a sending-behaviour signal — volume spikes, stale recipients — but Apple has never said so, and the label alone does not narrow the cause enough to act on. What it does tell you reliably is that this is permanent: the message will not be delivered, and resending it unchanged produces the same reply.
Why it happens
- A sending domain with no delivery history — including a domain's very first message, which is a common way to meet this code.
- A sudden change in volume or pattern from an address iCloud had seen sending little or nothing.
- Accumulated junk reports from iCloud users on earlier mail from the same sender.
- Mail to addresses that bounce or sit unread, which Apple explicitly asks senders to remove.
- A sending IP whose reputation at Apple is poor, independently of any public blocklist.
What to do
- Look at when the sending domain was set up and how much it has sent. A domain in its first week is the likeliest explanation by a wide margin.
- Do not retry. The code is permanent; repeats add rejections and change nothing.
- Verify SPF, DKIM, DMARC and forward-confirmed reverse DNS — Apple lists all four as requirements and a gap in any of them removes your best argument.
- Deliver the same message elsewhere to prove the content is fine before rewriting anything.
- Let the domain build history on receivers that accept it. iCloud follows.
- For a domain with real history behind it, contact icloudadmin@apple.com with the exact reply, the Txn ID, your sending IPs and the date it started.
Questions
How is HM08 different from CS01?
Nobody outside Apple knows, and the common explanation does not survive testing — we have identical messages that drew one code from one sending IP and the other code from a second IP within the hour. Both are permanent policy rejections and both call for the same response.
Is my IP blocked?
Not necessarily, and usually not. Apple's postmaster team describes these as specific to senders and campaigns. If the same IP is delivering other domains' mail to iCloud normally, the IP is not the problem.
Do I need to warm up the domain?
Sending gradually is good practice, but the thing that resolves this is history rather than a particular ramp shape. Ordinary traffic to receivers that accept you builds it.