Getting Remote Server returned '550 5.1.11 RESOLVER.ADR.ExRecipNotFound; Recipient not found by Exchange Legacy encapsulated email address lookup' when sending email

Dan Dierking 26 Reputation points
2022-06-23T11:54:01.47+00:00

Here is the back story. A client left our company. We hosted their emails on our hosted exchange 2016. Their emails are now on O365 with a new vendor. I deleted all of the email accounts in our hosted exchange using the exchange management shell (Can't access EAC at the moment and trying to figure out how to fix this issue) as well as the AD accounts. When we try to send email to the old client, we get this error: IMCEAEX-_o=First+20Organization_ou=Exchange+20Administrative+20Group+20+28FYDIBOHF23SPDLT+29_cn=Recipients_cn=165eaa177e6e462bacbdbd888964e213-Lara@datadynamics-inc.com
Remote Server returned '550 5.1.11 RESOLVER.ADR.ExRecipNotFound; Recipient not found by Exchange Legacy encapsulated email address lookup'

What's also interesting is that I am sending an email to lglauber@decipherglobal.com, not Lara@datadynamics-inc.com. I only deleted the decipherglobal.com emails from our server. We still have our datadynamics-inc.com email accounts on our hosted exchange.

I've read some articles about adding X500, but these email accounts are no longer on our hosted exchange, but now hosted by another provider in O365. We still need to be able to send emails to the old client. Is there a way to clear the cache or something for these email accounts in our hosted exchange environment using the exchange management shell since I can't get into EAC?

Exchange Server Management
Exchange Server Management
Exchange Server: A family of Microsoft client/server messaging and collaboration software.Management: The act or process of organizing, handling, directing or controlling something.
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Accepted answer
  1. Andy David - MVP 141.1K Reputation points MVP
    2022-06-23T17:16:05.49+00:00
    1 person found this answer helpful.

7 additional answers

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  1. Andy David - MVP 141.1K Reputation points MVP
    2022-06-23T12:08:27.237+00:00

  2. Andy David - MVP 141.1K Reputation points MVP
    2022-06-23T12:36:33.823+00:00

    Ok, thats a different error.
    Did you remove the accepted domain from your Exchange?

    MX20.datadynamics-inc.com

    is tellnig you that it doesnt exist.


  3. Andy David - MVP 141.1K Reputation points MVP
    2022-06-23T12:46:07.18+00:00

    Who manages the mail datadynamics-inc.com?
    Thats who is saying it doesnt exist. You may need to make a change there so the emails are correctly handled.
    RIght now that domain is using Barracuda. You may need to make a change there.


  4. Andy David - MVP 141.1K Reputation points MVP
    2022-06-23T13:26:34.593+00:00