HOW TO: Send as alternate email address

by Bharat Suneja on April 13, 2007

This is one of the more frequently asked questions in different forums – how do I send as an alternate address (aka proxy address or alias)?

You can use Exchange Server’s Email Address Policies (Exchange Server 2010/2007) or Recipient Pollicies (Exchange 2003), or the E-mail Addresses tab in EMC (Exchange 2010/2007) or Active Directory Users & Computers (Exchange 2003), to add additional email addresses for recipients (e.g. mailbox-enabled or mail-enabled users, Distribution Groups, mail-enabled Public Folders and Contacts). To find out how to add an additional email address for a recipient, see HOW TO: Add additional email addresses to a recipient.

Screenshot: E-mail Addresses tab in Exchange 2010 mailbox properties
Figure 1: You can add additional e-mail addresses for a mailbox from the E-mail Addresses page in mailbox properties

The email addresses are stored in a recipient’s proxyAddresses attribute in Active Directory. Recipients receive inbound email addressed to any of the email addresses in that attribute. (To be clear, messages addressed to any of the addresses received by the servers in your organization. To get the messages from external recipients to your servers, you’d still need the registered domain name(s), MX records, et al).

However, sending messages using any of those proxy addresses is a different story. When composing a new message, you can specify any of your email addresses (which exist in the proxyAddresses attribute). However, thanks to the voodoo magic that occurs between Outlook and Exchange, the From: address you specify automatically gets resolved to your Display Name (or more accurately, your user account) and gets sent using your primary email address. This is the address displayed using (upper-case) SMTP: in the E-mail Addresses tab.

This behavior also manifests itself when replying to a message that was received on an address other than the primary email address.

How do Outlook 2010 and Exchange 2010 behave?

Outlook 2010 allows you to specify a different from address.

  1. The From: field isn’t visible when composing a new message. To make it visible, go to the Options section and click From.
  2. Click From and select the alternate email address.

    If the address isn’t available in the list, select Send From Other E-mail Address window, type the email address in the From field.
  3. The result: Outlook 2010 changes the From address to the default email address:

Workarounds for sending mail using a proxy address

There are workarounds to accomplish this, but they are as annoying as the problem itself.

  1. Using additional mailbox or recipient(s)

    1. Create a new mailbox (you can also use other type of recipient objects such as Distribution Groups for this, but for this post I’ll assume you’re using a mailbox) for each address you want to use to send outgoing mail.
    2. Ensure this address is set as the primary address of the new mailbox.
    3. Assign the user Send As permission on the new account(s)
    4. When sending a new message, or replying to a received message, the user must manually populate the From: field in Outlook with the Display Name or SMTP address (or any other attribute that can resolve to the new account)
    5. Additionally, if you’re using a mailbox-enabled account for this purpose, the user can also open the additional mailbox in Outlook if they’re assigned Full Access mailbox permission to this additional mailbox, along with their primary mailbox. See HOW TO: Grant Full Mailbox Access permission.
    6. Alternatively, you can also redirect or forward inbound mail to the user’s primary mailbox by modifying Delivery Options in the properties of new recipient(s) created for this purpose.
  2. Using SMTP clients

    SMTP clients such as Outlook Express can be configured to send using the alternate email address. This can be equally annoying because every time a message needs to be sent as an alternate address, you will need to fire up Outlook Express (or your SMTP client of choice) to send the message.

  3. Using Address Rewriting

    On Exchange 2010/2007, you can use address rewriting. See a title=”More about Address Rewriting in Exchange 2010 docs” href=”http://technet.microsoft.com/en-us/library/aa996806.aspx”>Understanding Address Rewriting in Exchange 2010 docs. On Exchange 2003/2000, you can use the Microsoft Exchange Server Address Rewrite Tool to rewrite email addresses. Of course, these are administrator-controlled and applied on transport servers, so they apply universally to all messages that match rule conditions, and are intended to be used in scenarios such as mergers or company name and domain name changes that happen across an organization.

  4. Using a third-party tool – IvaSoft ChooseFrom

    IvaSoft makes nifty utilities for Exchange/Outlook that allow you to accomplish tasks that Exchange/Outlook do not allow you to do natively. Their ChooseFrom utility can be used to choose from any address listed in the proxyAddresses attribute, without the pain of the workarounds mentioned above. It uses a transport event sink installed on Exchange server, and is licensed per server.

    ChooseFromOWA, a separate version, enables this functionality from Outlook Web Access.

There’s no solution to this issue in Exchange Server 2007/Outlook 2007 as well (or in Exchange 2010/Outlook 2010). IvaSoft has released ChooseFrom for Exchange Server 2007/2010.

(As with most third-party software, install and test in a lab environment before you decide to install it on a production server.)

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