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Fundamentals of Mailbox Providers

Understanding the "Big 4" harbors. The email "sea" is dominated by a few major "harbor masters" (Gmail, Microsoft, Yahoo/AOL, Apple). This section explains that your #1 job is to understand their rules.

10 questions in this topic

What is a mailbox provider (MBP)? How do MBPs differ from ESPs? What are the major mailbox providers globally? How do mailbox providers filter and classify emails? What are provider-specific algorithms? How do MBPs use engagement and trust to rank emails? Why do different MBPs produce different inbox results for the same campaign? How do MBPs test new spam filters before rollout? How often do MBPs update filtering rules? How do providers balance user control vs algorithmic filtering?