Each Gmail account intended and designed for use by an individual user. If you have multiple users frequently accessing the same account from various locations, you may reach a Gmail threshold and your account will be temporarily locked down.
With the user-managed groups service, you can use groups to create "shared mailboxes" for your users. With a shared mailbox group, users can send and reply to messages using the group's email address rather than their own addresses.
If you're interested in using Google Apps as a CRM solution, please visit the Enterprise Solutions Gallery for a list of Google Enterprise Professional partners and other third parties.