4.1.4

Delayed Message: multiple mailboxes for recipient

The email message has not yet been delivered because the recipient's email address points to more than one email inbox and the recipient's email provider doesn't know which one to use.

Fixes

Check the recipient's email address for misspellings or missing letters. If an error is found, correct it in contacts list or address book for next time.

If necessary, contact the recipient another way (e.g., phone or text message) to confirm their email address.

4.1.4: Official Definition

4.X.X

[RFC3463] (Standards Track) from the The Internet Engineering Task Force (IETF) definition for codes that start with 4.X.X:

A persistent transient failure is one in which the message as sent is valid, but persistence of some temporary condition has caused abandonment or delay of attempts to send the message. If this code accompanies a delivery failure report, sending in the future may be successful.

X.1.X

[RFC3463] (Standards Track) from the The Internet Engineering Task Force (IETF) definition for codes that end with X.1.X:

The mailbox address as specified matches one or more recipients on the destination system. This may result if a heuristic address mapping algorithm is used to map the specified address to a local mailbox name.