Harrison Chirchir

Linux Administration, Cloud Operations, Mail Servers, Monitoring, Backups

Linux and cloud systems administrator at CloudSpinx. Runs the mail platforms, monitoring and backup estates behind client workloads, and the servers that keep answering when the power does not.

1 article

Articles by Harrison

Email 14 October 2026 · 7 min

Why Outlook Rejects Your Mail: SPF, DKIM and DMARC

Outlook now rejects unauthenticated bulk mail with 550 5.7.515. What SPF, DKIM and DMARC alignment it checks, and how Kenya's 39 banks set DMARC.

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