Email Hosting Glossary


Two-factor authentication (2FA), otherwise known as two-step verification or dual- factor authentication, is a security
process that requires the user to verify their credentials with two different authentication factors (e.g. a password plus either a security token or a fingerprint).

Bayesian Filter

A Bayesian filter is a program that uses Bayesian logic to evaluate the header and content of an incoming email message and determine the probability that it constitutes spam. If an email message scores too highly in Bayesian spam points, it is either delivered to a junk folder or rejected completely.

Branded Email Hosting

Branded (white label) email hosting refers to the ability to prominently display a company’s branding on hosted webmail accounts.

DDoS Attack

A distributed denial of service (DDoS) attack is when a system is attacked and overwhelmed with data from multiple machines (sometimes upwards of hundreds of thousands) distributed across the internet. The systems flood the target with superfluous requests from many different sources so legitimate requests cannot be fulfilled.

Email Address

An email address combines a sender domain with a unique user name chosen by the email user (e.g. [email protected]). An email address is often referred to in two parts: the “local part” (the email prefix), which is before the @ symbol; and the “domain”, which is after the @ symbol.


End-of-life (EOL) email refers to the final stages of an email  product’s existence. This means that the software will no longer be improved or actively maintained. Organisations are not advised to use EOL email products, because they pose a security risk and leave an organisation more vulnerable to hackers.


Greylisting is a method of identifying spam. A mail transfer agent using greylisting will temporarily ‘reject’ an email from a sender it does not recognise, while it collects details about the message (such as the sending server’s IP and the message envelope sender/ recipient). Legitimate emails will be resent as per their sending server’s retry rules and upon successful matching of the details collected.


Internet Message Access Protocol (IMAP) is a standard that was designed to allow multiple email clients to manage the same email account by maintaining the stored email on the server, rather than downloading messages directly to any one email client. IMAP is defined by RFC 3501.


JSON Meta Application Protocol (JMAP) is a protocol for synchronising data between a client and a server. Data includes, but is not limited to, email, calendars and contacts. JMAP is optimised for mobile and web environments and its goal is to provide a consistent interface for all data types.

Joe Job

Joe Job is an industry term for forged email spam. In order to hide their identity, the spammer or hacker fakes a genuine email address.


The Mail Abuse Prevention System (MAPS) provides antispam support by maintaining a Domain Name System-Based Blackhole List (DNSBL) or Real-time Blackhole List (RBL). This is essentially a list of locations on the internet reputed to send email spam.

MX Record

The mail exchanger (MX) record allows a single domain to run multiple mail servers. It does this by specifying which mail server is responsible for accepting the recipient’s incoming message.


A mail delivery agent (MDA), also known as a message delivery agent or local delivery agent, is the agent responsible for the delivery of emails to a local recipient’s mailbox.


A mail transfer agent (MTA), also known as a message transfer agent, is a type of software application that forwards inbound and/or outbound mail directly to the recipient.


A mail user agent (MUA), also known as an email reader, is a type of email client or software that uses collaborative computer environments to access and manage emails.

Multi-Part MIME

A multipart Multipurpose Internet Mail Extension (MIME) refers to emails that are sent containing both HTML and text formats. When a user receives a multi-part message, their device will automatically render to the format that the system has been set to show – either HTML or text.


Post Office Protocol (POP) is an application- layer internet standard protocol used to retrieve email from a server. The latest version, POP3, is defined in RFC 1939.


Role-based access control (RBAC) limits network access based on the user’s role within the company, so the user cannot operate beyond their jurisdiction.

Reverse DNS

A reverse DNS lookup matches an IP address to a domain name. This is different to a standard DNS lookup which matches the domain name to an IP address. Reverse DNS is a process for catching and preventing spammers with invalid IP addresses.


Simple Mail Transfer Protocol (SMTP) is an internet standard for electronic mail (email) transmission. It is a plaintext protocol, so you can just type commands from your keyboard and send an email. First defined by RFC 821 in 1982, it was updated in 2008 with Extended SMTP additions by RFC 5321, which is the protocol used widely today.


Spam refers to unsolicited, bulk emails that are usually unwelcome by the recipient and commercial in nature. Email users who initially opted-in to a mailing list sometimes also mark emails as spam if they are no longer interested in receiving those emails and find it easier to click ‘spam’ than to click ‘unsubscribe’.


The Sender Policy Framework (SPF) is a protocol that prevents email forgeries, by placing a strip of code within the email sender’s DNS information. That way, the incoming mail server can simply interpret the SPF record to authenticate the sender’s identity, before it reaches the recipient. SPF addresses the vulnerability of the SMTP email protocol, which does not have any authentication capabilities of its own.


Secure Sockets Layer (SSL) is a computer networking protocol that secures and encrypts data sent over insecure networks to avoid third-party eavesdropping. When personal information is sent over the network (such as a name, address and credit card details), only the user and secure server can interpret the data. Without this protocol, online shopping would be too risky and insecure. The easy way to tell if a website uses SSL certificates for authentication purposes is to look for the “https” in the URL.


Transport Layer Security (TLS) is a security protocol based on the SSL protocol. With the help of encryption techniques, TLS protects the privacy and integrity of data exchanges between communicating applications. TLS is the most widely-employed security protocol for web browsers, VPN connections, instant messaging, file transfers and more.


Web Distributed Authoring and Versioning (WebDAV), also abbreviated as DAV, is a protocol that facilitates collaborative authoring and editing between remote users over the web. CardDAV (an address book client/server protocol) and CalDAV (a calendar client/ server protocol) are extensions of WebDAV.    


Webmail is an email system where a user accesses their email through a web browser rather than via a desktop client.

The Ultimate Email Hosting Glossary

100 email hosting terms that telcos and hosting providers need to know

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