Recently, we had a requirement to send email to customers using a generic email address like firstname.lastname@example.org from Dynamics CRM (& Exchange Online).
The way we can implement this is through Shared Mailbox and Queue in CRM Online.
Log in to the Administration Portal
Select Shared mailboxes
Members can be added to the Shared Mailbox
Now back in CRM assign the email id to a particular queue.
Now sending an email activity with From as Queue and to as one of the user inside CRM.
Open the user’s mail box.
Make sure we have done Test and Enabled Mailbox for the Shared Email Box and have set Incoming and Outgoing Email as Server-Side Synchronization.
Hope it helps..