Your message did not reach some or all of the intended recipients.

[Rising Flight]

Hi experts

I have exchange hybrid environment.
I have created a shared mailbox(testshared-onpremises@mydomain.com) on premises exchange.
i have given SendAs permission to exchangeonline user by using the below shell command.

Add-ADPermission -identity "testshared-onpremises" -User exchangeonlineuser@mydomain.com -AccessRights ExtendedRight -ExtendedRights "Send As"

i have created a distribution list on onpremises exchange(onpremdl@mydomain.com) and added this shared mailbox (testshared-onpremises@mydomain.com) and exchangeonlineuser@mydomain.com to it.

when i am trying to send email to onpremdl@mydomain.com
i.e i am logged in as exchangeonlineuser i have selected From as testshared-onpremises@mydomain.com and sent an email to
onpremdl@mydomain.com i am getting below error. please help me

Your message did not reach some or all of the intended recipients.

      Subject: RE: test
      Sent: 18-Jul-18 12:41 PM

The following recipient(s) cannot be reached:

     

[#2]

You should provide a bit more details, such as, which recipients couldn't be reached. Are they members of onpremdl@mydomain.com etc.

[#3]

Shared Mailbox(testshared-onpremises@mydomain.com) is member of the DL(onpremdl@mydomain.com)
exchangeonlineuser@mydomain.com is cloud user who is a member of DL (onpremdl@mydomain.com)
exchangeonlineuser@mydomain.com is given as Send As permission to Shared Mailbox(testshared-onpremises@mydomain.com)