Error:
IMCEAEX-_o=HOSTING_ou=Exchange+20Administrative+20Group+20+28FYDIBOHF23SPDLT+29_cn=Recipients_cn=1049974d1dfsdfdsbae4d14979fe9987b-kingson+40cloudexchangers@com
Remote Server returned ‘550 5.1.1 RESOLVER.ADR.ExRecipNotFound; not found’
Cause:
Outlook uses X.500 address which is LegacyDN value to deliver the email from Microsoft Outlook which is also an auto cached entries, When this Legacy value changed outlook starts generating this NDR.
Resolution:
This involves some manual process.
IMCEAEX-_o=HOSTING_ou=Exchange+20Administrative+20Group+20+28FYDIBOHF23SPDLT+29_cn=Recipients_cn=1049974d1dfsdfdsbae4d14979fe9987b-kingson+40cloudexchangers@com
Remove – IMCEAEX
Result : _o=HOSTING_ou=Exchange+20Administrative+20Group+20+28FYDIBOHF23SPDLT+29_cn=Recipients_cn=1049974d1dfsdfdsbae4d14979fe9987b-kingson+40cloudexchangers@com
Replace all _ (Underscore) with (/) Slash
Result :
/o=HOSTING/ou=Exchange+20Administrative+20Group+20+28FYDIBOHF23SPDLT+29/cn=Recipients/cn=1049974d1dfsdfdsbae4d14979fe9987b-kingson+40cloudexchangers@com
Now, Replace +20 to Space
Result:
/o=HOSTING/ou=Exchange Administrative Group +28FYDIBOHF23SPDLT+29/cn=Recipients/cn=1049974d1dfsdfdsbae4d14979fe9987b-kingson+40cloudexchangers@com
Replace +28 to ( & +29 to )
/o=HOSTING/ou=Exchange Administrative Group (FYDIBOHF23SPDLT)/cn=Recipients/cn=1049974d1dfsdfdsbae4d14979fe9987b-kingson+40cloudexchangers@com
Remove domain.com (+40 is @)
Result:
/o=HOSTING/ou=Exchange Administrative Group (FYDIBOHF23SPDLT)/cn=Recipients/cn=1049974d1dfsdfdsbae4d14979fe9987b-kingson
Now this is your X.500 value add this as alias to affected mailbox to resolve this issue.
Reference : Click Here