Blog
SPF Too Many DNS Lookups: How to Fix the 10-Lookup Limit
October 7, 2026An SPF record can look perfectly valid and still fail authentication. One of the most common reasons is exceeding the SPF DNS lookup limit.
# DMARC
I Tested an LLM on Our DMARC Data. Here’s What I Found
October 1, 2026I connected Claude to the DMARKOFF MCP server and pointed it at one of our own domains: a newsletter subdomain sending through Amazon SES, 22,991 messages in the two weeks to 9 September, 53 distinct sending sources, p=none. I know every source on that domain, which makes it a fair test. I can check each conclusion the model reaches against what is actually happening
# DMARC
550 5.7.515 in Outlook: Why Email Bounces When DMARC Passes
September 30, 2026Your bounce reports SPF=Pass and DMARC=Pass. Outlook still refuses the message with 550 5.7.515. If the same diagnostic shows DKIM=Fail, those results are not contradictory.
# DMARC
Best DMARC Reporting and Monitoring Tools to Protect Your Domain
September 23, 2026It’s no secret that email authentication isn’t optional anymore. With mailbox providers like Google and Yahoo tightening sender requirements, companies are under increasing pressure to implement DMARC correctly and continuously monitor it.
# DMARC
Gmail 550 5.7.26: Fix DMARC and Authentication Rejections
September 21, 2026When Gmail rejects a message with a 550 5.7.26 error, the code alone does not tell you exactly what went wrong. The rejection may point to a DMARC policy issue, missing authentication, or an SPF hard fail. Identifying the exact diagnostic message is the first step toward fixing the problem without making unnecessary changes to your email setup.
# DMARC
DMARC Bounce Errors: Find the Cause and Fix Rejected Email
September 16, 2026An invoice bounces. A password reset never arrives. Your newsletter is accepted by one provider and refused by another. The delivery report mentions DMARC, but your DNS checker says the record is valid.
# DMARC
Queued Emails Explained: Causes, Fixes, and Prevention
You write an email, click send, and expect it to disappear into the internet within seconds. Instead, it sits in your Outbox with one frustrating word next to it: Queued.
# DMARC
What Is a Phishing Link? How to Identify It and How DMARC Helps
September 3, 2026Phishing remains one of the most common ways cybercriminals attempt to steal your credentials, financial information, and other sensitive data. Although phishing campaigns can take many forms, a phishing link is often the point where a deceptive message turns into an actual security compromise.
# DMARC
Why Your Business Should Budget for DMARC
September 2, 2026Companies use email for everything from internal communication and customer support to invoices, password resets, transactional notifications, and marketing campaigns. That dependence also makes email domains attractive targets for impersonation, phishing, and business email compromise.
# DMARC
No SPF Record Found? Causes, Fixes, and Best Practices
August 31, 2026Seeing a “No SPF Record Found” message during an SPF check usually means that the domain does not have a valid Sender Policy Framework record published in DNS. While this may look like a minor configuration issue, it can affect both email security and deliverability.
# SPF & DKIM