Protocol

/ɪksˈtʃeɪndʒ/

n. “Where your mail, calendars, and contacts meet.”

Exchange, short for Microsoft Exchange Server, is a messaging and collaboration platform that provides email, calendaring, contact management, and task scheduling for organizations. It is widely used in enterprises and integrates tightly with Microsoft Outlook, allowing a seamless experience across desktop, web, and mobile clients.

/ˌiː-ˈsɛm-ti-pi/

n. “Email with a few extra powers.”

ESMTP, short for Extended Simple Mail Transfer Protocol, is an enhancement of the original SMTP protocol used to send email over the Internet. While SMTP provides the basic rules for transferring messages from one server to another, ESMTP adds a suite of optional extensions that improve functionality, reliability, and security.

/ˈɛs-pi-ɛf/

n. “Verify the sender before you open the mail.”

SPF, short for Sender Policy Framework, is an email authentication method designed to detect and prevent email spoofing by verifying that incoming mail from a domain comes from an authorized IP address. It allows domain owners to publish a list of IP addresses or servers permitted to send email on their behalf in their DNS records.

/ˈdiː-mɑːrk/

n. “The rulebook for email trust.”

DMARC, short for Domain-based Message Authentication, Reporting & Conformance, is an email authentication protocol designed to give domain owners control over how email receivers handle messages that fail verification checks. It builds on existing standards like SPF and DKIM, providing both enforcement guidance and reporting.

/diː-keɪ-ˈaɪ-ɛm/

n. “Sign it so they know it’s really you.”

DKIM, short for DomainKeys Identified Mail, is an email authentication standard that allows senders to digitally sign their messages using cryptographic keys. The recipient server can then verify that the email was indeed sent by the claimed domain and that the message has not been tampered with in transit.

/stɑːrt-tiː-ɛl-ɛs/

n. “Upgrade the line before you speak.”

STARTTLS is a protocol command used to upgrade an existing plaintext communication channel—commonly in SMTP, IMAP, or POP3—to a secure, encrypted connection using TLS. Instead of initiating a connection directly over TLS, the session begins in cleartext and then negotiates encryption before transmitting sensitive data.

/ˌɛs-ɛm-tiː-ˈpiː/

n. “The mailman of the internet.”

SMTP, short for Simple Mail Transfer Protocol, is the backbone protocol for sending email messages across networks. It defines the rules and conventions for how email clients and servers communicate to relay messages from a sender to a recipient, often across multiple servers, until the final mailbox is reached.

/ˌeɪtʃ-tiː-ɛs-tiː-ɛs/

n. “Never talk unencrypted, even if asked nicely.”

HSTS, short for HTTP Strict Transport Security, is a web security policy mechanism that tells browsers to always use HTTPS when communicating with a specific site. Once a browser sees the HSTS header from a site, it refuses to make any unencrypted HTTP requests for that domain, effectively preventing downgrade attacks and certain types of man-in-the-middle attacks.

/ˌeɪtʃ-tiː-tiː-piː-ˈɛs/

n. “Talk securely or don’t talk at all.”

HTTPS, short for Hypertext Transfer Protocol Secure, is the secure version of HTTP, the foundational protocol of the web. It wraps standard web communication in an encrypted layer, usually via TLS, ensuring that data exchanged between a browser and server remains private and tamper-resistant.

/ˌpiː-oʊ-piː-ˈθriː/

n. “Download it, then it’s yours… maybe.”

POP3, short for Post Office Protocol version 3, is a standard protocol used by email clients to retrieve messages from a mail server. Unlike IMAP, which keeps messages on the server and synchronizes across devices, POP3 generally downloads emails to a single device and, by default, deletes them from the server, making local storage the primary repository.