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Our users have mutliple SMTP addresses in Exchange. We set one as their default reply-to.

From Outlook (for e.g., I'm using 2010 64 bit in Windows 7), in the e-mail compose window, there's a dropdown with all the user's SMTP addresses:

outlook From dropbox

However, when I chose one that is not my default reply-to address, I get an error like the following:

Delivery has failed to these recipients or groups:

Recipient's name
You can't send a message on behalf of this user unless you have permission to do so.
Please make sure you're sending on behalf of the correct sender, or request the necessary
permission. If the problem continues, please contact your helpdesk.

I don't understand. That's one of my SMTP addresses so why wouldn't I be able to send as it?

What would we have to do to allow allow all users to be able to send from any of their SMTP addresses?

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up vote 2 down vote accepted

This is not possible without a little bit of work... certainly not right out of the box.

See here:

The cleanest option is to set up pop or imap and add a second "account" in outlook that uses pop or imap and SMTP to send using the alternate address. But it is a manual setup for each address.

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I was afraid of that. But why would Outlook list your other SMTP addresses in Outlook? ...Not a real question... unless you're an MS software engineer :-). Figured that I'm missing something. – Belmin Fernandez Sep 14 '12 at 12:26
Not sure how you got that to happen, unless it is by entering the other addresses... When I click on the from box, I only see my primary address and "Other Email Addresses..." – Glenn Sullivan Sep 14 '12 at 12:28
Just checked with my colleague and he also didn't have anything else in that list. May have been that I added it a while back. Disappointing. – Belmin Fernandez Sep 14 '12 at 13:01

You can't really easily do this. When sending, Exchange will change your from address to your primary SMTP (reply-to) address as soon as you hit 'Send'. If you don't need to send too many messages from other addresses, one option would be to just change your primary SMTP address before sending the message to the address you need to send as. This is where Powershell makes it nice and quick:

 set-mailbox -primarysmtpaddress

You could then just rerun the command with your main address after you're done.

Not the solution you are probably hoping for, but a valid alternative.

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You can use a proxy SMTP address if the message is sent to Exchange through SMTP - in that case Exchange will not change the sender address and will let one of the proxy addresses to be used (you still cannot use an arbitrary address of course).

Proxy Manager ( does that - it is implemented as an Outlook addin, so to an end user it looks like the message is sent through Outlook like any regular message.

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