I love that this software allows you to have rules in place for what type of emails are allowed through each server. It helps limit spamming from certain IP's. The only thing i dislike about bouncer it takes up resources when running multiple servers with it. If you're looking at having more than 1 mail service provider then keep an eye out because if they don't work together well enough its hard to manage all those services without extra time spent configuring everything again and again. We had our own domain setup so we could use any hosting provider but wanted to be able to filter which providers would allow us senders sending newsletters/emails etc., via their SMTP relay.