Pay per send is a simple 'cost per email sent' plan. The unit cost is calculated at the end of each calendar month, and depends on how many emails you have sent that month.
Value plan is where you pay a fixed monthly fee, allowing you to send a specific number of emails per month.
dotMailer offered real support, value for money and were really keen to help me. Unlike some web-based companies, they're not afraid to pick up the phone -and their product delivers exactly what the website describes.
Prowill