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a couple of things are holding me back.

1. The majority of my clients are MS users so I need to be sure there is absolute compatibility both ways.

2. Integration with, or replacement of Outlook. Most open email readers that I have found are just that, email readers.

Outlook is integrated with contacts, calendar and tasks (which includes billing) and can send directly to One Note. Is there a FOSS that can replace Outlook 2007 and One Note???