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Custom domains, DNS records, MX, SPF, DKIM, DMARC, and Microsoft 365 domain onboarding.
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OOF is turned on but external senders aren't getting replies. Walk the external-replies toggle, the once-per-sender rule, the spam-filter override, transport rules that suppress OOFs, and the remote domain configuration that controls everything.
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An operator's guide to onboarding a custom domain to Microsoft 365 and configuring SPF, DKIM, and DMARC — including the seven anti-patterns that break enterprise mail, a verification command toolkit, and the cutover sequence that prevents delivery incidents.
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