Most network administrators are aware of how to check to see if your mail server is on a blacklist whether it be a RBL or DNSBL or any of its variations. The problem with most of them is that most of them check by IP Address. What about your domain reputation.
There are a number of sites that you can use to check your domain reputation to see if your email is or should be flowing properly. Following is a list that I use to check a domain for its reputation in regards to sending email effectively.
Before you whitelist a domain in Spam and Virus filter you should always check to determine the reputation of a domain. Additionally, you probably should not whitelist a domain that gives out free email accounts such as gmail.com , yahoo.com, hotmail.com etc. If you need to white list a sender from one of those domains you should whitelist only the user e.g. [email protected] , [email protected] , otherwise you may be opening up the floodgates of spam coming to your server.