The company I'm working at is having to go through each application that sends e-mails and verify compliance with CAN SPAM. One of the requirements is a corporate opt out system that ensures once someone has opted out, they will never get an e-mail from you again.
That can be tricky - say someone opts out of a newsletter you send. A year later, an employee sees your message board post asking for help with something that your product happens to do. The employee sends them an e-mail from Outlook, and BLAMO, you've just violated CAN SPAM (I think - IANAL).
So, I was thinking some smart person should write an SMTP proxy that verifies the recipient is not on the opt out list before sending the e-mail. Then you'd just need to do a DNS swap (mail.corporation.com becomes filteredmail.corporation.com, and the SMTP proxy is the new mail.corporation.com) and all your e-mail would automatically be filtered. The SMTP proxy would just need to be able to relay messages to the real SMTP service and to be able to read a few common data / file formats (SQL Server, XML, CSV, etc.).
That's not what we're doing - we're going through each application. Argh.