Send invoices and sales receipts via email. Supports PDF, HTML, and RTF. Personalize invoices and sales receipts using Crystal reports with your company logo, hyperlink, etc. Select Invoices or Sales receipts by customer or date range. Easily send all invoices for today, this week, this month, any date range, or for any given customer.

More info:
hxxp://www.synergration.com/InvoiceEmailer/default.htm