Blog

A dedicated sending IP sounds like the professional upgrade. For most senders it is a self-inflicted deliverability wound. Here is when each model is the right call, and the records you own the moment you switch.

A certificate chain that works in your browser can fail for API and mobile clients. Here is why chains break, why the failure hides, and how to verify one from outside.

A CAA record names which CAs may issue certificates for your domain. One DNS line closes off a whole class of mis-issuance. Here is how to use it.

SBL, CSS, XBL, and PBL each say something different about your IP. The Spamhaus return code is the diagnosis. Here is how to read it and who has to file the removal.

Let's Encrypt shut off its OCSP responders in August 2025, but most CAs still run theirs. Here is where revocation actually stands and how to check what your own certificates carry.

Quantum-resistant algorithms are landing in TLS now, not in some distant future. Here is what is changing for certificates and what to do before it reaches you.