What are common regional mailbox providers (GMX, Mail.ru, ProtonMail, Zoho, Yandex, etc.)?

Common regional mailbox providers include GMX and Web.de (Germany), Mail.ru (Russia), Yandex (Russia and CIS countries), ProtonMail (Switzerland, privacy focused global), and Zoho (business email globally). Each serves significant user populations in their respective regions or niches.

These providers often dominate local markets where global providers have less penetration. GMX and Web.de together serve tens of millions of German speaking users. Mail.ru is the largest email provider in Russia. Understanding which regional providers matter depends on your audience geography.

Regional providers typically implement standard email protocols and authentication but may have unique filtering approaches, language specific content analysis, and different complaint handling processes. Deliverability optimization may require provider specific attention when these domains represent significant portions of your list.