Blacklist and whitelist
What are blacklists and whitelists in email marketing and how they can help reducing your spam rate.
An email blacklist is a public list of email senders (usually identified with their IP) which are considered source of unsolicited bulk messages – that is, spam.
How spam filtering works with black lists of denied IPs and white lists of legitimate email accounts and IPs.
One of the most popular ways to fight spam is certainly to rely on the Spamhaus Project. Here's how to check if your IP is ok.
The only way to build a white list for effective email campaigns is to get permission-based contacts.