There is a seamless integration between Exchange and OCS. so the exchange client (Outlook) and OCS client (MOC) needs to share the DLLs before they could access each others information. This article talks about those outlook DLLs which communicator uses for different purposes.

The following (Outlook) files are held "in use" when Communicator 2005 or Communicator 2007 is running:

• Contab32.dll ---This is for the address book.

• Emsmdb32.dll ---This is an exchange extensions dll used for the Mailbox

• Mspst32.dll -- For store access (PST, and I believe OST)

• Mso.dll -- general Office functionality common to all applications, for example, toolbars, file open/save UI, etc.    

• Olmapi32.dll

• Riched20.dll -- rich-text editing code

If Communicator 2007 is running, the following file is also held "in use"

•Msores.dll -- similar to mso.dll above, but res files should contain all of the language-specific resources, such as language-specific strings that appear in
dialog boxes, errors, etc.

If there is any problem with Outlook-communicator integration, the very first thing we need to check if these two are updated with latest patch or not!

Communicator and outlook both should be properly updated in order to ensure that both perform the integration features without any problem.