I am integrating salesforce with order, delivery, and invoice information from SAP.  I want this information to be available to our customer portal users.  The way that our SAP data is set up, we have a one-to-one relationship between order, delivery, and invoice line items, so the integration becomes MUCH easier when we can just pass all the line items to one custom object rather than trying to integrate header info and line items into 6 different related custom objects. 

This solution would make for simple reports that our portal users could understand.  However, I also want portal users to receive email alerts for things such as new deliveries, invoices due in a few days, etc.  Each delivery or invoice has a few line items, though, so in this case users would get an email for every line item.  For example if a shipment was sent to them with three line items, they would get three line items when it shipped, and then three more when the invoice was due.  Is there a way to limit the number of emails sent to a user to one a day?  Does anyone have any other ideas of a good way to accomplish what I want?  Any help would be much appreciated!