Managing IPs manually is same amount of work as managing iptables - see updated question. Yeah, integrating identity providers could work, knowing recipient em

Managing IPs manually is same amount of work as managing iptables - see updated question. Yeah, integrating identity providers could work, knowing recipient email addresses and that they use particular services. However that has some complexity/libraries and as with that - vulnerabilities all over again. I just don't want to think/expose attack surface and give possibilities for automated attacks to leak personal data. Or lets say it like that - I trust iptables more than myself integrating identity provider or depending on some library. Actually this is what onedrive/photo galleries etc. does when you share files/folders - generates some magic link that penetrates auth. However it's the same story - I trust complex system (that may have well known vulnerabilities and I was on a vacation) less than iptables.