Brian St. Marie - Sr. Systems Engineer
Oftentimes, users want the ability to send email from a different address using Microsoft Outlook. With a Microsoft Exchange server, it's very easy to add additional email addresses for users to receive mail, but not so easy to allow them to send from those addresses.
Each mailbox on an Exchange server has a primary address. This is the address from which all mail is addressed when sending through this mailbox. So even if you add aliases to this mailbox which allow it to receive mail on a different address, the user will not be able to send from that address.
Unfortunately, despite this being a highly requested feature by users for many years, Microsoft has yet to create any way to allow users to do this natively in Outlook and Exchange.
One workaround is to create a second "dummy" mailbox and assign the alias address to this mailbox instead. Permissions can them be added to this dummy mailbox to allow the user to choose the dummy mailbox address as the "From" field on new emails. The dummy mailbox can then be configured to forward any incoming email to the alias to the user's primary mailbox. This will work, but it is a bit clunky, and requires the user to select the alias address out of the Global Address List each time they want to send an email with the alias address.
Likewise, a distribution list can be used to accomplish the same thing. In addition, using a distribution list can allow more than one person to receive mail on the alias address, which can be useful for generic email aliases like support@ or sales@. However, it still requires the users to select the alias address from the Global Address List each time they want to send from the alias.
The last option is to use a third party product to add functionality to Outlook which will allow the user to select a mailbox alias as their sending address as they compose a new email. This setup is the most straightforward and intuitive for users, but it does require additional cost and software.
As multiple addresses per user becomes more and more common, hopefully Microsoft will add this functionality into future versions of Outlook and Exchange. For now, while there are no perfect solutions for this common problem, there are workarounds which can do the job.