To prevent your IP from being blacklisted by an anti-spam organization, please follow these steps:
- Make sure all the IPs are set with proper PTR records.
- Configure the proper value for spam filters.
- Make sure all the local computers which use mailboxes are secured with a well-known Internet Security Anti-virus application & Microsoft Security Essentials (for Windows platform).
- Make sure all the login details for WebMail & Hosting are secured - use complicated and strong passwords.
- Make sure the web scripts are secured with a proper permission level and a proper code. e.g. unwanted code/scripts/pages - should be removed. As well as web's CMS e.g. WordPress & Joomla are up-to-date.
- From time to time, check if your IPs are blacklisted here.
- Check the Mail Queue from time to time to see any possible spamming activity or compromised user mailbox.