Sometimes connections stops

==== Required information ====
- iRedMail version: 0.8.5
- Store mail accounts in which backend (LDAP/MySQL/PGSQL): LDAP
- Linux/BSD distribution name and version: Ubuntu 12.04 LTS
- Related log if you're reporting an issue:
====

In rare ocasions we face strange issue one of our customers cannot sent/receive messages.
It takes about hour or two. Then he can send/receive messages normally.
Customer has couple mailboxes and in most cases uses Outlook (2010).

Thank You for ideas.
Tas