From what I am seeing there is no account integration.
There is email integration via IMAP.
There are some add-on modules that will do some integration to AD and Exchange (the Executive Assistant Module ...
http://www.3com.com/products/en_US/detail.jsp?pathtype=purchase&tab=features&sku=3C10450A) (The Call Center Module ...
http://www.3com.com/products/en_US/detail.jsp?pathtype=purchase&tab=features&sku=3C10440)
I am not seeing anything for account integration to AD/Exchange or LDAP support unless this is included in the modules mentioned and just not documented ... but I doubt that, you probably have to configure the accounts and then enable the integration to the external sources.