How do I check if my domain or IP is blocklisted?

Free third-party lookups will check the major lists in one pass:

• Check both - your sending IP address and your domain, since they are listed separately.
• Read the reason - each list publishes why it listed you and how to request removal.
• Fix the cause first - delisting without fixing the compromised account or the bad list simply relists you.

If you send through a provider like Microsoft 365 or Google Workspace, the IP is theirs; a listing usually points at your domain or your content.