BaccS allows to send notifications to specified users when a Contractor or a Customer perform particular action (create a new job, deliver an assignment, register an invoice, edit own profile, etc.). List of users who get notifications is specified by Send notifications checkbox in the User editing form.
After setting up list of users who receive notifications, create a user with Vendor or Customer role to allow them to log in into your portal. When one of supported actions will be performed by such users, each user eligible for receiving notifications will see popup notification window (both in Windows and Web versions) and a yellow 'bell' icon with a number of unread notifications will appear at status bar:
Double click on notification to view corresponding assignment, contractor or customer editing form.
Click Dismiss to delete notification, or select Snooze time and click Snooze to view same notification later.
Same behavior in web-version:
Take a note that each user eligible to receive notifications will receive similar notification. If one user deletes own notification, other users won't be affected and still will be able to view own notifications.