A “welcome list” is a list of IPs & domains that would only be blocked under exceptional circumstances.
That isn’t to say that these IPs and domains don’t ever send bad mail, but just that they’re run by legitimate entities.
And so, blocking them outright would cause significant false positives.
Why is a welcome list essential for a blocklist provider?
Welcome lists prevent blocking legitimate emails sent from “mixed” sources.
Google sends a not-insignificant amount of spam. They have numerous services like Google Drive that are regularly abused to host phishing and malware. Still, if their outbound IPs or one of their sub-domains were blocked, it would cause a lot of legitimate mail to be rejected. The blocklist wouldn’t be very useful.
So instead of blocking these by IP address or domain name, additional scrutiny can be placed on other attributes. A few that can be used that wouldn’t cause other legitimate emails to be affected are, for example:
- an email address
- cryptocurrency wallet
- short URL
- drive URL
- DKIM domain
- Any other blockable item within the message.
So, to build a good blocklist, you need an even better welcome list to prevent false positives that would be caused if you indiscriminately listed any IP address or domain name that was hitting spam traps.
Available Welcome Lists
Welcome list providers will have stringent requirements for being included. They will closely monitor the output from each listed entity to ensure that it is compliant with its sending policies, not hitting spam traps or receiving any complaints from users. Otherwise, it will be quickly removed.
SparkPost Reputable Sender Accreditation Program
Abusix Mail Intelligence includes our welcome list data and DNSWL and Certified Senders Alliance data.