Historically, Exchange has used a user’s primary SMTP address as the From address when sending messages. Other SMTP addresses assigned to a user (e.g., proxy addresses, also known as aliases) were ma...
Updated Oct 21, 2024
Version 11.0
Blog Post
This has been working for years. In Outlook desktop or Outlook on the Web, the user will need to add the address to the FROM menu using the OTHER Email Address dialog the first time they send from it.
Microsoft recently added the ability for this to happen automatically, that's all. It's already released. Remember, the alias must be listed under the individual user. If not, Send As configuration will be required.
2. https://www.slipstick.com/outlook/office-365-exchange-send-proxy-addresses/
3. https://www.slipstick.com/office-365/send-messages-secondary-office-365-exchange-addresses/