I am currently running a hybrid MS 365 environment using AD connect to sync.
User mailbox was migrated from on-prem Exchange server to Exchange Online
I remove the license and lock the account via AD
I send email to user A and it still delivers.
User was created in AD and after the AD Sync I created the mailbox on M365.
I remove the license and lock the account.
I send email to user A I get an NDR.9 Which is the desired result .
Why are my migrated accounts still accepting mail?
We don't delete accounts, we disable them for audit and record keeping