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550 5.1.1 iCloud: user does not exist

550 5.1.1iCloud Mail recipient does not existPermanent: retrying will not helpFrom iCloud Mail

Example
550 5.1.1 <user@example.com>: user does not exist

What it means

This is Apple’s plain unknown-recipient answer. The enhanced code 5.1.1 is “Bad destination mailbox address” in RFC 3463, and the reply comes at the RCPT TO stage, before your server sends the body. Apple checked its directory and found no live mailbox for the address. Nothing here is about your reputation or content.

Behind an iCloud address there is an Apple Account with iCloud Mail switched on. The address can stop existing when the person deletes the account, removes an alias they once created, or never finished setting up iCloud Mail. People who use iCloud+ custom domains can also remove an address from their domain, which produces the same answer for that domain.

This differs from a 5.2.2 mailbox full bounce, where the account exists but cannot take more mail, and from Apple’s bracketed policy tags such as [CS01], which are refusals of a valid recipient.

Likely causes

  • A typo in the local part, or a domain mix-up such as icloud.com typed where the person uses me.com or mac.com.
  • The owner deleted their Apple Account or turned iCloud Mail off.
  • An alias the user created inside iCloud Mail was later deleted.
  • A custom domain on iCloud+ where the address was removed or the domain was moved to another provider while its MX still points to Apple.

How to fix it

  1. Check the address character by character against a recent message the person sent you, including which Apple domain they use.
  2. Ask the person through another channel for a current address. Do not keep retrying the old one.
  3. Remove or suppress the address in your mailing list or CRM after a single hard bounce like this one.
  4. If the domain is a custom one, look up its MX records: if they still point at iCloud but the owner says they moved, they need to update DNS.

Checks that apply

  • MX Lookup Shows whether the recipient domain really uses iCloud’s mail exchangers, which matters for custom domains on iCloud+.
  • SMTP Diagnostics Connects to the domain’s mail server and shows its banner and TLS, so you can see you reached Apple and not an old host.
See the example diagnosed

The classification runs without network lookups and we never store your paste.

FAQ

Could Apple be wrong about the user not existing?
It is very rare. Apple answers from its account directory, so a 5.1.1 here almost always means the address is gone or mistyped.
Will retrying later help?
No. A 550 5.1.1 is permanent. If the person has a new address, use that; retrying the old one only hurts your list hygiene.
Does this bounce hurt my sender reputation?
A single one does not. A high rate of unknown-user bounces tells providers your list is stale, so suppress the address right away.

All 191 bounce codes