Hello All
i am on project for migrating 2000 mailboxes to Exchange online, i have two Exchange forest environments on premises running Exchange 2013 and 2016 respectively, i am facing a unique problem of NDR these days . scenario is as follows.
For new joiners i am creating user account in AD(on Premises) and allow it to sync and then create Mailbox on cloud.
Challenge - existing On premises users are getting NDRs for mails sent to newly created mailboxes on cloud.
can someone help me to resolve this.
