Check whether your mail server's IP address (or domain) is on a DNS blacklist — the reason legitimate email sometimes lands in spam or gets rejected. Enter an IPv4 address, or a domain to check its A record.
What is a DNS blacklist (RBL)?
A DNS-based blacklist (DNSBL), also called a real-time blackhole list (RBL), is a published list of IP addresses known for sending spam. Mail servers check incoming connections against these lists and reject or flag mail from listed addresses. If your sending IP gets listed, your email deliverability drops sharply.
What to do if you're listed
Identify the cause — an open relay, a compromised account, a misconfigured server, or shared-hosting neighbours.
Fix the underlying problem so you don't get relisted immediately.
Visit the blacklist's website and follow its delisting / removal procedure.
Make sure your domain has valid SPF, DKIM and DMARC records. SPF / DKIM / DMARC