The following non-delivery reports:

The recipient email address was not found in the recipient email system. Microsoft Exchange will not try to redeliver this message for you. Please check the email address and try resending this message, or provide the following diagnostic text to your administrator.

Recipient email address was not found

The email address you entered couldn't be found.  Please check the recipient's email address and try to resend the message. If the problem continues, please contact your helpdesk.

The email address you entered coudn't be found

mean that Exchange server was unable to resolve the recipient's email address and find the recipient in the system.

The Diagnostic information for administrators section may contain the following errors:

550 5.1.1 RESOLVER.ADR.RecipNotFound
RESOLVER.ADR.RecipNotFound

This non-delivery report is usually generated in the following cases of internal delivery (to the domain hosted with Intermedia):

  • the email address in spelled incorrectly
  • the recipient's mailbox no longer exists
  • the MX records for the recipient's domain are pointing to a 3rd party server and the recipient is hosted on that 3rd party server but split domain option isn't enabled. To resolve the issue, enable the split domain option

550 5.1.1 Recipient address rejected: User unknown in the relay recipient table
Recipient address rejected: User unknown in relay recipient table

This non-delivery report is usually generated in the following cases of delivery from an external domain:

  • the email address in spelled incorrectly
  • the recipient's mailbox no longer exists

IMCEAEX-_O=OEXCHXX_OU=EXCHANGE+20ADMINISTRATIVE+20GROUP+20+28FYDIBOHF23SPDLT+29CN=RECIPIENTS_CN=username@internal #550 5.1.1 RESOLVER.ADR.ExRecipNotFound
IMCEAEX x500 issue

This non-delivery report is generated when:

  • an old x500 cache entry is used by the sender's Outlook client/OWA.

    There are 2 ways of resolving the issue:

    • ask the sender to remove the autocomplete cache entry
    • if the recipient email address was previously assigned to another object (used as alias of another mailbox or used to be a distribution list, public folder etc. which was later deleted and then recreated), contact Support and provide the full body of the bounce back message. Support will assign the old x500 entry to the new object
      Example: you deleted an Exchange mailbox and created a Distribution List with the same email address
  • you replied to a message imported from another mail system that had an internal reply-to address. The resolution is to type the email address manually.
  • the Outlook contact is corrupt. Check the address listed for the contact and correct it, or recreate this contact.