Free Postmaster Tools including SPF Analyzer, Blacklist Checker

We recently released our Postmaster Tools for postmasters & email deliverability professionals. Hop over to the tools section and give them a try!

Free Blacklist Checker

As we outlined in our introduction to blacklists, a blacklist is a spam-blocking list used to reject and filter mail. Mailbox providers use these lists to identify problematic senders and reject mail. Being listed can dramatically alter your ability to deliver mail to your recipients. 250ok’s free Blacklist Checker can be used to check your IP or domain against 30+ major blacklists.


Free SPF Analyzer

SPF (Sender Policy Framework) is used to prevent sender address forgery. According to, most abusive emails carry fake sending addresses. SPF enables brands and marketers to specify their sending policy so mail services can verify where the message came from. You can quickly analyze and verify your SPF records using 250ok’s SPF Record Analyzer.

DMARC Wizard

DMARC (Domain-based Message Authentication) standardizes how receiving mail servers perform email authentication. Mailers and marketers can use DMARC policies to tell inbox providers like Gmail, AOL, and Hotmail that their messages are protected with SPF and DKIM. With our DMARC Wizard, you can analyze your DMARC record or create a DMARC policy for your domain.

IP Range to CIDR / CIDR to IP Range

CIDR, or Classless Inter-Domain Routing, is an expansion of the IP addressing system that allows for a more efficient allocation of addresses. The IP Range to CIDR tool enables you to convert an IP range to a CIDR notation, or visa versa.

DNS Lookup Tool

Our free DNS lookup tool will list and organize your DNS records in priority order.

We’ll be adding more tools in the near future. If you have a free tool that you would like to see, please let us know!


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