Background: I work at a company with several confidential business partnerships that require employees to appear as though they work for another company/brand and use multiple domains via email in accordance with whatever brand they happen to be representing at the time. We've had moderate success with most of this requirement so far. (I have an Exchange 2013 on-premises DAG environment in a one forest, one domain architecture, but multiple SMTP domains)
Problem: When a user sets up an out-of-office to reply externally, Exchange auto-replies only from the primary SMTP address of the user.
Example: John Doe emails a customer from jdoe@CompanyB.com and goes out of office. The customer replies to the email and receives an out-of-office reply from jdoe@CompanyA.com instead; breaking our contractual obligation of maintaining the confidential partnerships.
Question: Does anyone know how/if this can be fixed so the out-of-office sends from the address that was originally sent to instead of only sending from the primary SMTP alias of the user?
Restrictions: I'm hoping to avoid configuring multiple mailboxes or 1-to-1 shared mailboxes for my 500+ users, and also hopefully avoiding creating a second domain or standing up more servers for this fairly trivial (from a technology standpoint) issue.