Publish an email newsletter. Promote advertising opportunities. Find cool new sites. It's just like any other paid autoresponders. You can add or delete the email addresses.
Prospects can remove themselves with one click.
All original inquiries forwarded to your email address. Daily activity logs delivered to your email address. Then you know what it's like. AD on top of your messages, bottom of your messages. If you assume above statistic holds true for email marketing, you have to email tons of messages to your inquiries.