DigInterface Blog
Tutorials and reference articles on DNS, email authentication, networking and developer tools.
SPF Record Length Limits: The 10 DNS Lookup Rule Explained
SPF records that trigger more than 10 DNS lookups return permerror and break deliverability. Here's why the limit exists, how to count your lookups, and how to fix it.
MTA-STS Explained: Enforcing TLS for Inbound Mail
MTA-STS lets your domain insist that other mail servers use TLS when delivering to you — closing the longstanding STARTTLS downgrade hole. Here's how it works and how to deploy it.
How to Read an Email Header (Gmail, Outlook, Apple Mail and What It All Means)
Every email carries hidden headers that show where it came from, how it travelled, and whether it passed authentication. Here's how to find them and what they mean.
DKIM Signature Failed: 7 Common Causes and How to Fix Them
DKIM signature failures fall into a small set of recurring causes. Here are the seven you'll actually hit in production, with how to diagnose and fix each.
How to Read a DMARC Aggregate Report (the XML, decoded)
DMARC aggregate (RUA) reports are XML files that look intimidating but tell a simple story. Here's how to read one, what each field means, and what to act on.
What is an SPF Softfail? Understanding the ~all Qualifier
SPF softfail (~all) tells receivers an email probably isn't authorised, but to deliver it anyway. Here's what it means, when to use it, and when -all is safer.