Emails

In short: Individual electronic messages delivered via a mail protocol (e.g. SMTP) — the specific “letters” within the mail system.

In more detail: An email consists of a header (sender, recipient, subject, routing information) and a body (the actual content, possibly with attachments). Between the sender’s mail server and the recipient’s mail server, there can be several intermediate stations (relays), each logged in the header.

In Depth

A typical email header contains considerably more than just sender and recipient:

From: sender@emzett-digital.com
To: recipient@example.com
Subject: Your order
Date: Thu, 17 Sep 2026 10:06:16 +0200
Received: from mail1.example.com by mail2.emzett-digital.com ...
Received: from client.example.com by mail1.example.com ...

Every station that forwards an email adds its own Received header at the top — this lets the complete delivery path be traced backwards, which helps with spam and fraud analysis. The body is structured via MIME encoding if the mail contains several parts (e.g. plain text plus an HTML version plus attachments) — MIME allows arbitrary binary data (images, documents) to be embedded in text form within the otherwise text-based mail.

The actual transport between mail servers runs via SMTP; the recipient retrieving the fully delivered mail, by contrast, runs via a separate protocol like IMAP or POP3.

See also: Mail, Mail Server