Go to http://www.mxtoolbox.com
This test will list MX records for a domain in priority order. The MX lookup is done directly against the domain’s authoritative name server, so changes to MX Records should show up instantly. You can click Diagnostics , which will connect to the mail server, verify reverse DNS records, perform a simple Open Relay check and measure response time performance. You may also check each MX record (IP Address) against 147 DNS based blacklists . (Commonly called RBLs, DNSBLs)
ABOUT BLACKLIST CHECK
This test will check a mail server IP address against 147 DNS based email blacklists. (Commonly called Realtime blacklist, DNSBL or RBL). If your mail server has been blacklisted, some email you send may not be delivered. Email blacklists are a common way of reducing spam. If you don’t know your mail server’s address, start with a MX Lookup. Or, just send an email to firstname.lastname@example.org
ABOUT SMTP DIAGNOSTICS
This test will connect to a mail server via SMTP, perform a simple Open Relay Test and verify the server has a reverse DNS (PTR) record. It will also measure the response times for the mail server. If you don’t know your mail server’s address, start with a MX Lookup.
ABOUT EMAIL HEADERS and Analyzer
This tool will make email headers human readable by parsing them according to RFC 822. Email headers are present on every email you receive via the Internet and can provide valuable diagnostic information like hop delays, anti-spam results and more. If you need help getting copies of your email headers, just read this tutorial.
ABOUT SPF RECORDS
Sender Policy Framework (SPF) records allow domain owners to publish a list of IP addresses or subnets that are authorized to send email on their behalf. The goal is to reduce the amount of spam and fraud by making it much harder for malicious senders to disguise their identity.
ABOUT DNS LOOKUP
This test will list DNS records for a domain in priority order. The DNS lookup is done directly against the domain’s authoritative name server, so changes to DNS Records should show up instantly. By default, the DNS lookup tool will return an IP address if you give it a name (e.g. www.example.com) If you give it an IP address it will return a hostname based on the reverse DNS lookup.