Here is something which I face today, implemented complete new forest with exchange 2016, since the ADMT migration tool doesn’t completely support Windows server 2016 and complexity of cross forest migration, we have decided for manual migration from old forest (abc.com) to new forest (xyz.com). All the active directory objects are created on new forest with .csv approach and mailbox migration is client driven (from outlook ost to pst migration and pst to ost migration on new mailbox)

Issue: –

Users are unable to reply old email and it was failing with NDR report

Error: –

IMCEAEX-_O=abc_OU=EXCHANGE+20ADMINISTRATIVE+20GROUP+20+28FYDIBOHF23SPDLT+29_CN=RECIPIENTS_CN=MUSTAN+20ALI775@xyz.com

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

 Findings: –

• Able to send email after manually selecting email address from GAL
• Successfully able to send email from OWA

Cause: –

• Each email content information of complete path of LegacyExchangeDN form ADSI edit
• old emails LegacyExchangeDN is pointed to old domain

Solution: –

• Since the old domain controller was accessible, I have copy the LegacyExchangeDN information from recipient properties in ADSI edit
• Create X500 record and past old LegacyExchangeDN as email address in new exchange 2016 mailbox email address properties

Manual way to create X500 address (from msexchangeguru) (Link)

We need to add a new X500 address to the user mailbox from Exchange Management Console. To do that, we need to first create it in the right format.

First step is to get rid of the _ and convert them to /

/O=EXCH/OU=EXCHANGE+20ADMINISTRATIVE+20GROUP+20+28FHSDHJF23GHYED+29/CN=RECIPIENTS/CN=RON+2EMayers@contoso.com

Now the tricky part:

/O=EXCH/OU=EXCHANGE+20ADMINISTRATIVE+20GROUP+20+28FHSDHJF23GHYED+29/CN=RECIPIENTS/CN=RON+2EMayers@contoso.com

Look closely and you see some numbers like +20, +28 etc… Wondering what they are?

+20 is a SPACE

+28 and +29 are ( and ) respectively

+2E is .

So the actual X500 address to be added will look like this:

/O=EXCH/OU=EXCHANGE ADMINISTRATIVE GROUP (28FHSDHJF23GHYED)/CN=RECIPIENTS/CN=RON.Mayers@contoso.com