Skip to content
From an administrator, for administrators

Secure email takes attention to detail.

I deliberately use DANE when running my email services. Certificates and TLSA records must continue to match after a change. I wanted to automate the check that they do. That became Sendequelle.

I am Norbert Sehm. With Sendequelle, I make experience from running my own email services useful to other administrators, IT service companies and providers.

How it all began Explore all features
Norbert Sehm Founder of Sendequelle
Norbert Sehm holding certificates at the presentation with BSI President Claudia Plattner and representatives of eco and Bitkom.
Norbert Sehm at the certificate presentation with BSI President Claudia Plattner and representatives of eco and Bitkom as part of the Email Security Hall of Fame.
From my own operations to everyday practice

It started with a script.

  1. Recognising the dependency

    Consider certificate renewal and DANE/TLSA together, and include a check that they match in the monitoring.

  2. Automating the checks

    I wanted a regular, joined-up view of the checks I could already run individually on Linux.

  3. Building Sendequelle from that idea

    Today, the platform combines continuous monitoring, report analysis and tools for investigating specific problems.

The starting point

Renewal was automated. Checking the match was not yet.

Secure email communication is part of my commitment as a provider. That is why I deliberately use DANE on my distributed email systems. The relationship matters: the certificate or key in use must match the published TLSA association, including after a change.

Certificate renewal with Certbot was automated. Checking whether the certificate and TLSA record still matched was not yet. When customers reported missing messages, I realised that this dependency also needed automated monitoring.

I often used tools such as MXToolbox for individual checks. Yet I could already run those technical queries myself on Linux. Why not write a script to carry out these checks regularly and bring the results together?

That script grew into Sendequelle: a tool that makes technical relationships visible and helps me spot changes earlier. Today, I am making that experience useful to other administrators, IT service companies and providers.

The experience behind it

I know the work behind a functioning mailbox.

I have run my own email services for many years, including emailn.de, Skymail and Firemail. Behind every message are people who depend on their communication: a reply, a proposal or an important appointment.

For me, proper authentication, secure transport and reliably operated infrastructure belong together. That experience goes directly into Sendequelle.

What this means for you

More clarity. Less time piecing together clues.

The needs of my own operations became tools that help you spot changes, investigate problems and work together on the next steps.

Explore all features

Keep track of changes

Monitor DNS, mail servers, certificates and DANE/TLSA to make issues affecting secure email transport visible.

Explore monitoring

Understand your sending sources

Bring DMARC and TLS-RPT reports together: which sources send for your domains, where does authentication fail and where do transport errors occur?

Explore report analysis

Investigate a message

Analyse submitted headers and email files, trace recorded transport hops and compare messages with your own references.

Explore email forensics

Make sense of delivery failures

Analyse DSN delivery notifications and selected Postfix log excerpts to turn technical error information into an understandable delivery diagnosis.

Discuss delivery diagnostics

Manage abuse reports in one place

Bring reports together, track their status and document your decisions. You remain in control of the action taken.

Discuss abuse management
My commitment

A tool that helps when it matters.

I want you to spot changes in your infrastructure earlier and take informed action. To spend less time on recurring checks. And, whenever possible, to hear about the next problem from your monitoring.

Secure email is part of my daily work. Sendequelle is my tool for it.

Norbert Sehm Founder of Sendequelle

Get to know Sendequelle with your own infrastructure.

Explore the features, start your trial or talk to us about the needs of your email operations.

Try free for 14 days Explore all features Get in touch