In the email world, most anti-spam programs use lists as part of their effort to figure out who’s legit and who’s not. A blacklist is the worst and can affect your ability to send email to nearly anyone. A whitelist is maintained by a single person or company, but it says you are approved and can send email to them anytime. A greylist, no surprise, is somewhere in between.
Blacklists are managed by a variety of spam-prevention services. They flag people, websites, and servers that are known spammers. Many anti-spam programs rely on these lists to filter out bad email. If you are caught on one, you will undoubtedly have problems delivering your message. Since different email servers rely on different lists, you may find most email gets through and only a few people have problems. Get on a big enough list – or several lists – and the number of issues will increase.
Even the innocent get blacklisted. For example, a spammer may “spoof” your email, making it appear that you are a spammer even though messages come from a completely different source. If you start getting bounce-back messages as mentioned above, that make it appear you sent large batches of obscene or get-rich-quick emails to people you don’t know, that’s the most likely cause. There’s no way to prevent this; wait a couple of days and it will usually subside.
Another frequent problem arises because small businesses often share email servers via a hosted service. If someone else on your server is a spammer, everyone is in danger of being blacklisted. If this happens, you’ll start getting bounce-back messages with a spam-related error message.
Blacklist removal can be extremely simple or extremely complex – it all depends on the list, but blacklists assume you are guilty until proven innocent.
Greylists are less serious but can be equally frustrating because they are harder to track down. Many large organizations will use these to filter email from senders they haven’t seen before. As long as your message isn’t spam, this will more likely delay your message than completely block it. However, if you need quick response and the email doesn’t arrive for a full day, it creates a significant communications obstacle.
When the delay is a one-time occurrence and your next message gets through, there’s no need to do anything. Keep in mind you may encounter delays with several recipients; it’s only cause for concern if you run into multiple delays with the same person, or even the same company.
If your message never arrives, contact your recipient’s email administrator and request to be added to their whitelist. That’s their list of approved email addresses that always get through.