I'm facing a challenge with my organization's email security policies. We block any network communication from outside the US, but recently, we've noticed we're not receiving emails from companies we normally communicate with. After some investigation, I found out that these emails, despite being from US companies, are being routed through European servers. Has anyone experienced a similar issue? We're currently spot-allow listing blocked IPs we've found in our firewall logs, but I'm hesitant to implement a broad CIDR filter for all O365 mail servers. It seems like I'm just enabling individual IPs as needed, but that doesn't feel sustainable.
3 Answers
I totally get your hesitation about blanket CIDR filters. However, it could actually be a lot easier than going IP by IP! That approach can become a total nightmare as those IPs frequently change. Maybe consider trusting the O365 IP ranges and shifting your focus to enhancing security around identity and authentication instead of just blocking based on location.
Yeah, relying on whitelisting specific IPs is not sustainable. It's a better strategy to block traffic from countries known for high spam rates, like China or Russia, while allowing trusted channels. This could streamline your process while maintaining security.
Just echoing what others have said—it's really not a scalable solution to let in individual IPs. Over time, you could trust the main O365 IP ranges. This way, you can reinforce security with solid identity checks rather than just geographical filters.
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