advanced email newsletter tool

there is many email newsletter software out there. but I need some little special features. the main goal is NOT to send emails to many recipients. and it is NOT about SPAM problems or getting black listed... it is about: being able to schedule every complety different email every X minutes [X is random i.e. between 5, 7, 9, 11, 15, 19, 31 minutes] emails are automatically generated with random subject (var1) and attachment (var2) var1 is maybe listed in a txt file var2 is a folder on a server, via ftp or on a local PC where the new tool is running