Infrastructure
Oct 7, 2026·~3 min read
How to View Email Headers in Gmail
View email headers in Gmail, Outlook, and Apple Mail: open Show original, find Authentication-Results, and read spf=, dkim=, and dmarc= without guessing.
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ZeroHook Blog
Fixes, not fluff. DNS security and compliance guides for IT managers who already know the acronyms.
Infrastructure
Oct 7, 2026·~3 min read
How to Read Gmail Postmaster Tools
Read Gmail Postmaster Tools: verify your domain, domain reputation, spam rate near 0.3%, and authentication charts versus what headers show on a single message.
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Infrastructure
Oct 4, 2026·~4 min read
What Is an MX Record?
What is an MX record? Learn how mail exchanger priority works, why SPF does not replace MX, and three ways to verify routing before receipts and alerts stop arriving.
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Infrastructure
Jun 21, 2026·~4 min read
Fix Gmail 550 5.7.26 Auth Errors
The 550 5.7.26 authentication required bounce means Gmail rejected your message before inbox placement. Fix SPF, DKIM, DMARC alignment, and envelope-from settings for M365 and Google Workspace.
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Infrastructure
Jun 21, 2026·~6 min read
SPF Passes but Mail Lands in Spam
When SPF passes but mail lands in spam, DMARC alignment, missing DKIM, or envelope-from mismatch is the usual cause. Diagnosis and fix steps for Gmail, M365, and ESP relay sends.
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Infrastructure
Jun 21, 2026·~11 min read
Gmail Spam Filter 2026: 35 Mail Failures
Gmail and Microsoft spam-folder legitimate mail for authentication, DNS, reputation, and list-hygiene reasons most admins never audit. All 35 failure modes and fixes in one guide.
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