Enter a domain (or an email address) to look up its MX records, resolve each mail server to its IP addresses and reverse DNS, and check every mail-server IP against major blacklists. Use it to diagnose why mail from a domain is bouncing or landing in spam.
MX (Mail Exchanger) records tell the rest of the internet which servers accept email for your domain, and in what order of preference. When someone sends mail to you@example.com, their server looks up example.com's MX records, picks the lowest-priority (most preferred) host that answers, and delivers there. If those records are missing, misconfigured, or point at a server whose IP has landed on a spam blacklist, your inbound and outbound mail can be delayed, bounced, or silently filtered to spam. This tool shows your full MX fleet sorted by priority, resolves each mail server to its IPv4 and IPv6 addresses, checks reverse DNS (PTR), and tests every mail-server IP against major blacklists in one view.
Enter a domain name (or an email address, in which case we use the part after the @) and click Look Up MX. The tool queries your MX records, sorts them by priority, resolves each host to its IP addresses, looks up reverse DNS on the primary IP, and runs a blacklist check on each mail-server IP. Green means clean, red means listed. If any IP is listed, click through to the full blacklist report for that IP. Deliverability warnings are listed at the bottom.
Lower MX priority numbers are preferred, so your main mail server should have the lowest value. Keep at least one backup MX on a separate host so mail is not lost when the primary is down. Every sending mail server should have a valid reverse DNS (PTR) record that matches its hostname, since missing PTR is one of the most common reasons mail gets rejected. Never point an MX record directly at an IP address, since MX must name a hostname. If a mail-server IP shows as listed, use the Details link to see which blacklist and how to request delisting. On shared or hosted mail platforms your MX IP is shared with other customers, so a listing may reflect a neighbor rather than your own traffic.
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