How iCloud Mail answers a verification check
icloud.com, me.com and mac.com addresses are all served by Apple's mx01 and mx02.mail.icloud.com. Apple accepts existing mailboxes and refuses missing ones with a permanent 5xx rejection, and Apple notes that most of its rejections include a URL with more information. Most iCloud addresses get a definite verdict.
iCloud+ subscribers can also use custom domains on Apple's mail servers, and two Apple privacy features create addresses you will see in signups: Hide My Email addresses at icloud.com, and Sign in with Apple relay addresses at privaterelay.appleid.com. Both forward to a real inbox. Relay addresses only accept mail from senders registered with Apple's private email relay service.
iCloud Mail replies and what RocketVerifier returns
Each SMTP reply maps to one status and sub-status. Replies about the probing server are never counted against the address.
| Reply | Result | What it means |
|---|---|---|
| 250 2.1.5 OK | deliverable none | The mailbox exists. |
| 550 5.1.1 recipient rejected | undeliverable mailbox_not_found | No such mailbox. |
| 421 / 450 temporary deferral | unknown greylisted | Retried automatically, up to three times. |
| 550 5.7.x policy rejection | unknown blocked | About the sender. Not charged. |
What RocketVerifier does differently for iCloud Mail
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Apple gets its own receiver class
Custom domains on iCloud+ are detected from their MX records and verified with the same Apple profile as icloud.com, not as an unknown custom server.
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Careful pacing, one catch-all probe
The Apple session profile uses a few recipients per session and a single catch-all probe, inside a dedicated per-IP rate budget.
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A block is never a bad address
Replies about the probing IP, rate or policy are returned as unknown with the blocked sub-status and never charged. Only an explicit mailbox answer becomes deliverable or undeliverable.
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Deferrals retried for you
Temporary deferrals are retried automatically, up to three times about ten minutes apart, before a final result is returned.
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No email is ever sent
The SMTP conversation stops at RCPT TO, before DATA. Your recipients never see a probe.
Sending to iCloud Mail: what to get right
- Treat Hide My Email and Sign in with Apple relay addresses as the customer's chosen address. They reach a real person.
- To email privaterelay.appleid.com addresses, register your sending domains and addresses in your Apple Developer account, or Apple's relay rejects the mail.
- Apple asks senders to use SPF and DKIM, publish a DMARC policy and reverse DNS, and track temporary and permanent SMTP errors. Apple offers no feedback loop, so watch unsubscribes and bounces closely.
Keep reading
Sources
- Apple: iCloud Mail postmaster information
- Apple Developer: Configure private email relay for Sign in with Apple
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