Hello webb72475,

SourceOne supports two options when working with Exchange and Active Directory environments.  Only the Exchange Resource Forest configuration is supported for multiple Active Directory forests.  I have included a section from our Admin Guide page 36:

(Sorry for the poor formatting, the table looks much better in the documentation)

Table 3 Active Directory forest configurations

Active Directory forest configuration

Single Forest

A single Active Directory forest containing one or more

domains. Each domain contains one or more Exchange

servers. A common global address list (GAL) is used for

all domains.

This is the simplest topology and is recommended by

Microsoft in the document Active Directory Forest

Topologies which is available online at:

http://technet.microsoft.com/en-us/library/bb124765(EXC

HG.80).aspx.

EMC SourceOne configuration

Single or multiple domains in a single forest are

supported by EMC SourceOne as described in

the EMC SourceOne Email Management

Installation Guide.

Multiple Forests (Exchange Resource Forest)

Multiple Active Directory forests are used. One forest is

dedicated to running Exchange and hosting Exchange

mailboxes. The user accounts associated with the

mailboxes are contained in one or more other separate

forests.

This configuration is also referred to as a Dedicated

Exchange Forest configuration.

EMC SourceOne configuration

Only EMC SourceOne Offline Access should be

installed in the forests not containing the

Exchange server.

All EMC SourceOne components must be

installed in the same Active Directory forest as

the Exchange server. Refer to the EMC

SourceOne Email Management Installation

Guide for information on installing these

components.

“Configuring Exchange PST processing across

Active Directory forests” on page 37 describes

the additional tasks you need to perform if you

are processing PST files across multiple forests.

Multiple Forests (Exchange Cross-Forest)

Multiple Active Directory forests are used. Each forest

contains an Exchange server and the user accounts for

users of that Exchange server.

This configuration has several disadvantages and

requires extensive synchronization of active directory

objects across forests and requires replication of other

data.

EMC SourceOne configuration

Not supported by EMC SourceOne.

Only the Exchange Resource Forest

configuration is supported for multiple Active

Directory forests.

Hope this helps!

Thanks,

Brad