If you’re using Apple’s Mail.app in conjunction with an Exchange server where you have an account that is also configured to use an alias address, you may have encountered an odd problem where anytime you hit “Reply All” to a message, your alias address is included on the CC line of the email.

This had been happening to me for quite some time.  Instead of searching for a solution and resolving the issue, I dealt with it by simply deleting the address on the CC line before sending.  This morning, though, I decided to take a few minutes to try to permanently resolve the issue.

It turns out it’s a pretty easy fix, likely caused by an odd quirk in the way that Mail.app handles Exchange account information.

When you set up your Exchange account on OSX, the information about your configuration to the mail server that the application uses on each startup is stored in a .plist file called “Accounts.plist”.  This file is located in the /Users/{username}/Library/Mail/V2/MailData/ directory.  The quickest way to get to and edit this file is to use Finder’s Go>Go To Folder menu, and type in the folder name.  When you see the Accounts.plist file, open it for editing (make sure that you’ve shut down Mail.app before attempting to edit).

A .plist file is a simple XML file used by OSX apps to store and read configuration data on startup.  Because these files are XML based, you should be able to read and edit them with any capable text editor.  I prefer Bare Bones Software’s BBEdit but any text editor should work.

The basic structure of this XML file is as follows:

<key>DeliveryAccounts</key>

<array>

<dict>

Account Information

</dict>

</array>

Search the various accounts in your DeliveryAccounts array until you find the Exchange account, listed as an “EWSAccount” in the Account Type section of the XML.  Within this block of XML code, you’ll see a key named “EmailAddresses”, followed by an array with the email addresses associated with this account listed.  If you’re experiencing the self-CC problem, it’s unlikely that the alias that you use with your Exchange account is listed here.

Just add an additional string value to the email address array, inserting your alias address between the <string>..</string> blocks.

Here is a before and after of my EWSAccount section:

Before:

After:

After making this change, save the file, restart Mail.app, and try reply-all.  You should no longer see the self-CC appear on the CC line of the email.