I have disabled a mailbox on exchange and added its email address as an alias for another mailbox. The alias is working fine when sending email from an external domain, but it isn't working when sending from the same domain. It returns the error:

Remote Server returned '550 5.1.1 RESOLVER.ADR.ExRecipNotFound; not found'

The email address smtp:msouza@contosocorp.com is showing on the mailbox's addresses.

How can I fix this?


This is happening because the auto-complete cache in Outlook and Outlook Web App uses the x500 email address instead of the SMTP (also know as LegacyExchangeDN), and this address was not found as the error is saying.

To avoid this you need to add the LegacyExchangeDN as a email address to the desired mailbox too. You can find the DN in the error message:

Take this line: IMCEAEX-_o=Contoso+20Corp_ou=Exchange+20Administrative+20Group+20+28FYDIBOHF23SPDLT+29_cn=Recipients_cn=Magalhaes+20B+2E+20Souza+2C+20Mariana9ca@contosocorp.com

  1. Remove IMCEAEX-.
  2. Remove the @contosocorp.com at the end.
  3. Replace _ for /.
  4. Replace +XXfor the corresponding character on the ASCII table where XXis the Hexdecimal value. (Example: +2E = alt + 46 or .).
  5. Add X500: at the beginning.

Commons appearances:

  • +20 = (blank space)
  • +28 = (
  • +29 = )
  • +2E = .
  • +2C = ,

You will have something like this: X500:/o=Contoso Corp/ou=Exchange Administrative Group (FYDIBOHF23SPDLT)/cn=Recipients/cn=Magalhaes B. Souza, Mariana9ca

Then you add it as another Email Address:

Set-Mailbox administrator -EmailAddresses @{Add="X500:/o=Contoso Corp/ou=Exchange Administrative Group (FYDIBOHF23SPDLT)/cn=Recipients/cn=Magalhaes B. Souza, Mariana9ca"}

Source: https://support.microsoft.com/en-us/kb/2807779

  • 1
    Another option would be to put a forward on the disabled mailbox to send email to the other mailbox. That could be easily reversed if the disabled mailbox needs to come back in to use. – Sembee Oct 7 '16 at 18:55

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