not able to send email to another on same server

==== Required information ====
- iRedMail version:      v0.8.6 (MySQL)
- Store mail accounts in which backend (LDAP/MySQL/PGSQL):
- Linux/BSD distribution name and version: Ubuntu 12.04.4 LTS
- Related log if you're reporting an issue:
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For some reason I'm getting clients that use Outlook not able to send emails to other emails on the same server.  Anyone know why this would be?