SugarCRM - Zimbra Module
The motivation for this integration is a simple one. For sales people, customer service people and to a lesser extent, marketing people, SugarCRM and Email clients like Outlook and Zimbra are both productivity tools. They help people manage their work, store their contact information, and manage their communication. Sugar goes further than just that, but essentially crosses over into the email client domain with contact details, email, calendars and appointments.
The use case for SugarCRM, where ,say, a sales person uses SugarCRM to manage their communications, appointments and contacts pertaining to sales opportunities through Sugar, and uses, say Outlook for everything else (colleagues, business partners etc) is unsatisfactory to say the least. The idea that Sales people will be willing to give up their nice GUI Outlook mail for the Sugar mail module is unlikely, given its limited functionality. A Sales person while working in Outlook, is outside the context of their CRM, and as a result you looses all the advantages that CRM gives you. There are plug-ins and modules that let you sync between the two, but, because they require the user to actually perform the sync (or identify what to sync), are unsatisfactory, and would be dismissed by users as just a hassle, and not intuitive.
The obvious solution (but perhaps not an easy one) is to bring the functionality of a CRM system and a great email client together in the one productivity tool. Thus the integration of SugarCRM and Zimbra.
Because the functionality of a mail client is a subset of the functionality of a CRM, it makes sense to integrate the mail client into the CRM. (Not the other way around).