Email testing tools (e.g., Mailchecker)
Email testing tools (e.g., MailChecker, MailTester, or MailCheck) are online services used for the pre-send technical analysis of emails before a mass mailing. They simulate the process of a mail server receiving a message and generate a detailed report that helps identify configuration errors and other issues that can negatively impact deliverability.
Regular use of these tools allows for the control and optimization of key message elements, such as:
Correctness of technical configuration: Verification of SPF, DKIM, and DMARC authentication.
Quality of headers and message structure: Assessment of compliance with technical standards.
Content and link analysis: Checking the correctness of HTML code and verifying all links for security.
Domain and IP address reputation: Checking for presence on public blacklists (RBLs).
Verification process using Mailchecker as an example
Go to the MailChecker website and copy the unique, generated test address (in the @mailchecker.net domain).
In your sending system, send a standard test message (identical to the one you send to your recipients) to the copied address.
Wait for the system to analyze the message and generate a report.
After a few minutes, refresh the MailChecker page or click the Check output button to see the result.
Interpreting the result
The analysis result is presented as a percentage score and a detailed report for individual sections.
Overall scoring
89-100% – Correct configuration: All key technical elements are configured correctly. The risk of deliverability problems is minimal.
69-89% – Good configuration with minor remarks: Most settings are correct. An analysis of sections with a lower score is recommended for further optimization.
39-69% – Configuration requires improvement: Errors or deficiencies that may negatively affect deliverability have been detected.
29-39% – Significant configuration errors: The message has serious technical flaws that will likely cause delivery problems and may lead to it being classified as spam.
0-29% – Critical configuration: Fundamental technical errors or serious reputation problems have been identified. Sending messages without implementing changes is highly risky.
Description of report sections
Headers
Analysis of the message's technical headers.
Correctness of SPF, DKIM, DMARC; Domain Alignment; presence of the List-Unsubscribe header; Message-ID; use of an S/MIME certificate.
Body
Analysis of the email's content and structure.
Compliance with HTML standards; text-to-image ratio; correctness and security of all links (URL test); detection of elements like iframe/JavaScript.
ISP & DNS settings
Assessment of the domain's DNS and mail server configuration.
Correctness of the PTR record (Reverse DNS); DMARC policy; existence of an MX record for the domain; compliance with the TLS protocol; presence of a BIMI record.
Virus scan and antiphishing
Security analysis of the message for malware and phishing.
Scanning content, attachments, and links for viruses, malware, and phishing elements.
Blacklist
Checking for the presence of the sender's domain or IP address on global blacklists (RBLs).
Status on key, public anti-spam lists; potential reasons for the block.
Systematic testing is a key element in maintaining the high technical quality of email communication. It allows for the ongoing verification of configuration correctness, identification of errors, and assessment of reputation, which directly translates into higher deliverability.
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