Most Email Verifiers Lie About Outlook Addresses. Here's Why.

If you have been running cold outreach in 2025 or 2026 and your bounce rates suddenly jumped from 1% to 5-7% despite using a "premium" verification tool, this post is for you. The short version: most email verification APIs cannot reliably verify Microsoft 365 / Outlook mailboxes anymore, but they will not tell you that. Instead, they return valid or catch_all and let you find out at send-time. This post is about why that happens and what you can actually do about it. I run cold email infrastruc