Postmaster Toolbox - (the short list)
Commissioning a mail server is initially not terribly complicated, but at the latest when it comes to keeping an eye on your reputation, or if you want to implement authentication measures like SPF (Sender Policy Framework), DKIM (DomainKeys Identified Mail) or DMARC (Domain-based Message Authentication, Reporting and Conformance), it becomes considerably more complex and there’s no way around using appropriate analytical and other tools. Fortunately, there are several free possibilities available in the Internet. The websites are all in English.
Cisco Talos Intelligence
At https://talosintelligence.com/, alongside a range of blog articles, white papers and presentations on the topic of e-mail security, there is also the possibility to check the reputation or your own domains and IP addresses and to see how the provider of a spam filter assesses your emails.
As the name says, at https://mxtoolbox.com there is a whole collection of useful tools. Ranging from multi-faceted DNS query tools to blacklisting checks, there are also tools for analyzing e-mail headers. You can find answers here to many different questions.
Free Postmaster Tools from 250ok
As well as their fee-based tools, 250ok offer a range of helpful tools free of charge at https://250ok.com/tools/. A special mention should go to the “Gmail Tab Tester,” which you can use to find out to which tab in the Gmail surface an e-mail will be sorted before sending a campaign.
On the website of the DMARC-specialists dmarcian (https://dmarcian.com) you can find tools relating in particular to DMARC and the associated technologies SPF and DKIM, which considerably simplify the implementation of DMARC.
This organization has taken on the task of encouraging the spread of DMARC. The website at https://dmarc.org/resources/deployment-tools/ contains, alongside many articles, tutorials and statistics, a collection of tools for generating, checking and parsing DMARC records, and much more.
Internet.nl email Test
An initiative of the Dutch government and industry makes a simple-to-use test available at https://internet.nl/test-mail/ to evaluate a range of standards. Are the mail servers reachable with IPv6? Is the domain signed with DNSSEC? Are my e-mails authenticated and does my mail server use transport encryption? The test provides answers to all these questions and details on the assessment and the meaning of the results for the individual points.
Sending e-mails is easy. Sending large volumes of e-mails professionally is not. The technologies necessary to ensure a well-functioning platform have their quirks.
However, with the help of the tools mentioned above they can be mastered. Given that these tools can be used free of charge, there’s no reason not to try them.