OS X Mavericks :: Exchange Email Account Aliases In Mail For Mac

I've always used Mail in Mac OS X but one day I decided I would try Outlook 2011 so I could manage rules and filters without having to go to OWA. I was not very happy with Outlook 2011 so I removed it and decided to go back to Mail for Mac OS X. Since trying Outlook 2011, I'm having problems setting up the Exchange account in Mail.My company uses first.last company.com and flast company.com for our email address/alias.When I setup the account, auto discovery finds everything just fine and logs me in and downloads all the mail, rules, filters, etc. stored on the server. The problem is in Internet Accounts in System Preferences, I now see two Exchange accounts. One for first.last and another for flast. since mail seemed to be working fine, but one day I noticed something when I did a reply all to a mail message. It included myself in the reply to fields. I thought maybe it was a setting in Mail that I overlooked when setting up the Exchange account. As it turns out though, the problem is that the first.last account is now somehow the default mail account on Exchange and the flast is what I'm replying with.Checking System Preferences, I noticed that the first.last Exchange account doesn't have checks in the selection boxes for Mail, Contacts or Notes, but it does for Calendars and Reminders. However the flast is exactly the opposite; it has checks in the selection boxes for Mail, Contacts and Notes, but not Calendars or Reminders.

When I try to enable Mail, Contacts or Notes in the first.last Exchange account I get an error dialog stating "There was a problem setting up the account. An unknown error occurred."I experience this on multiple computers, including an iMac 27", iMac 24" and MacBook Pro 17".I'm using Mac OS X Mavericks 10.9.4 and iCloud for my home accounts and connecting to an Exchange 2010 work account.

Info:
iMac (24-inch Early 2009), OS X Mavericks (10.9.4), Core 2 Duo 3.06Ghz