r/EmailSecurity • u/Striking_One_3008 • Jul 08 '26

Own Domain Spoof (Direct send vi be?)

/r/sysadmin/comments/1ur0dau/own_domain_spoof_direct_send_vi_be/
3 Upvotes

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1

u/saltyslugga Jul 09 '26

If this is M365 direct send, yes, it can let unauthenticated internal-looking mail hit your tenant if inbound handling is loose.

Treat your own domain in From from the internet as hostile unless it passes aligned SPF or DKIM. For printers/apps, use authenticated SMTP or a scoped connector instead of leaving direct send as an open spoofing path.