What to do if mails you send bounce
If your mail server IP is listed in a DNS blacklist (DNSBL), a majority of your emails will bounce – especially from large providers such as Google, Hotmail, etc.
You can check if your mail IP is blacklisted by performing a search here.
If your IP is listed, it means that:
- Someone was able to exploit a web application vulnerability and upload a spam script
- Someone stole the login details to an email account, and is sending out spam through that account.
Just go to each of the site that you are listed and ask to be removed.