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

Question

Hello,

We have a requirement to offboarding around 200 mailbox from exchange online to Microsoft Exchange On-premises. We have a hybrid environment and we offboarding all 200 mailboxes successfully. After offboarding, we are facing a massive issue.

When we send a new mail to offboarded mailbox, we can send it successfully but when we reply our previous mail loop we are getting the following NDR:

_o=ExchangeLabs_ou=Exchange+20Administrative+20Group+20+28FYDIBOHF23SPDLT+29_cn=Recipients_cn=7bf52caf6c6943a3aa4e2ef7bdc6a82b-Microsoft+20S@primebank.com.bd
Remote Server returned '550 5.1.11 RESOLVER.ADR.ExRecipNotFound; Recipient not found by Exchange Legacy encapsulated email address lookup'

We raised a ticket to Microsoft regarding this issue and they suggested us to manually type the mail address. So, it is not possible to us to 200 mailbox type manually and another thing is that we also receive outside mail, so it is not possible to inform all other organization to type manually the mail address. So, it's not a suitable solution for us. Please suggest something which we can do centrally. It's become a massive issue right now. So, please suggest something as early as possible. It's totally a business critical issue. Thanks in advance.

Answer 1

Hi @Md.Rubiat Haque,

I read some thoughts on the X500, hope it helps.

When it is an internal recipient, but not for external recipients. ->Create an X500 proxy address for the old LegacyExchangeDN attribute for the user

For external recipients you can try creating distribution groups with an x500 Address in and a forward to the correct external mailcontact.

Other cases:

->https://www.reddit.com/r/exchangeserver/comments/jvsyb1/recipient_not_found_by_exchange_legacy/

->https://community.spiceworks.com/how_to/185726-fixing-ndr-errors-after-deleting-re-creating-a-user-550-5-1-11-resolver-adr-exrecipnotfound-recipient-not-found-by-exchange-legacy-encapsulated-email-address-lookup

(Please Note: Since the web site is not hosted by Microsoft, the link may change without notice. Microsoft does not guarantee the accuracy of this information.)

Regards

Shaofan

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Answer 2

Check these blogs for your issue - Cannot remove accepted domain and Error: 550 5.1.1 RESOLVER.ADR.ExRecipNotFound

Please Note: Since the web sites are not hosted by Microsoft, the links may change without notice. Microsoft does not guarantee the accuracy of this information.