What Are Email Headers?
Email headers are the metadata on every message — sender, route, timestamps, spam verdicts. What each header means and how to read the full set.
Glossary
Email, defined.
Short, straight answers to the terms you hit when dealing with email — the file formats, the protocols, and the headers inside every message.
What Is a .EML File?
One email message in the internet's standard RFC 822 format — headers, body, and attachments in a single portable file.
IMAP vs POP3: What's the Difference?
IMAP syncs your mailbox across devices; POP3 downloads it to one and usually deletes the rest. Which to pick, the ports, and why neither one is a backup.
What Is an MBOX File?
MBOX stores a whole mailbox in one plain-text file. Where .mbox exports come from — Takeout, Apple Mail, Thunderbird — and how to open or split one.
What Is a .MSG File?
A .msg file is one Outlook message in Microsoft's proprietary binary format. Why nothing else opens it, and how to view or convert one without Outlook.
What Is a PST File?
A PST is Outlook's Personal Storage Table — one proprietary file holding mail, calendar, and contacts. How to open one, size limits, and when not to trust it.
What Is RFC 822?
RFC 822 is the 1982 standard that defined the email message format — headers, blank line, body. Why the name survives, and where .eml and MIME fit in.