What is POP3? A Clear Guide

POP3 (Post Office Protocol) downloads email from a server to a single device, typically removing it from the server. IMAP has largely replaced it.

Why it matters

Knowing POP3 helps you send mail that lands in the inbox. See the deliverability checklist.

How Rainmail helps

Rainmail sends from your own domain on a dedicated, isolated IP with SPF, DKIM, DMARC, reverse-DNS and managed warm-up handled for you, plus an AI watching list health and deliverability — and it welcomes senders SES, SendGrid and Mailchimp reject, from $8. Run the free checker or see plans.