What do Gmail, Yahoo, and Outlook actually do?

**Gmail**, **Yahoo**, and **Outlook** (**Microsoft**) are the largest mailbox providers, collectively hosting billions of email accounts. They receive your emails, filter spam, organize inboxes, and provide webmail and app interfaces for recipients to read and manage messages.

Each operates massive infrastructure handling billions of messages daily. They maintain independent spam filtering systems using machine learning, user feedback, and reputation data. **Gmail**'s filters emphasize engagement and tabs. **Microsoft** uses **SmartScreen** and **Safe Links**. **Yahoo** applies similar but distinct approaches.

These providers shape deliverability standards through market dominance. When **Gmail** requires DMARC alignment or **Microsoft** tightens bulk sender rules, the entire industry must adapt. Understanding each provider's specific requirements and quirks is essential for reaching their users.