Fixes, not fluff. DNS security and compliance guides for IT managers who already know the acronyms.
Gmail shows an unverified sender warning when DMARC, SPF, or DKIM alignment fails on your From domain. Fix steps for M365, Google Workspace, Mailchimp, and HubSpot relay mail.
When DMARC alignment fails but SPF passes, your envelope-from or DKIM domain does not match the visible sender. Quick diagnosis from Authentication-Results and ESP fix steps.
Choosing a DMARC policy is not a one-time DNS edit. None monitors, quarantine filters, reject blocks unauthenticated mail. Rollout order, pct= staging, and provider-specific pitfalls for 2026.
Move from monitor-only DMARC to p=reject in eight weeks using aggregate reports, pct= staging, and sender inventory. Standard path for SMBs on M365, Google Workspace, and ESP relay mail.
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.
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.
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.
Get the latest security alerts and analysis from the ZeroHook team.
