What Is Email Software? Definition, Types, Functions and Examples

Email software is any program used to write, send, receive, store or organise email. In everyday use it means an email client: the app you read mail in, such as Outlook, Apple Mail, Thunderbird, or Gmail in a browser or on your phone.

The term is wider than that, though. The mail servers that move messages between companies are email software. So are the marketing platforms that send newsletters to thousands of people at once. This guide gives the definition, the main types side by side, what email software actually does, how it works underneath, and real examples of each type.

Email software definition in one line#

If you need a single sentence: email software is the set of programs that create, deliver and display electronic mail, from the app on your screen to the servers that route a message to the right inbox.

Most confusion comes from one brand covering several layers at once. Gmail, for example, is a provider (Google's servers hold your @gmail.com mail), webmail (gmail.com in a browser), and a mobile email client (the Gmail app). All three are email software, but they do different jobs.

What are the main types of email software?#

Email software falls into a handful of types. The first three are what a person uses to read their own mail. The rest work behind the scenes or serve businesses sending mail at volume.

Email client vs webmail vs email provider#

These three get mixed up most, because people rarely see them separately. The provider owns the mailbox and your address. The client, whether a desktop app, a phone app or a browser tab, is only the window you look through.

That split is why you can change apps without losing anything. Connect Apple Mail or Thunderbird to a Gmail address and you see the same messages, because they still live on Google's servers. Change provider, on the other hand, and your address and stored mail have to move with you.

Webmail is a real email client, not a lesser category. It runs in the browser instead of being installed. A dedicated app usually adds better offline reading, system notifications and handling of several accounts in one place. The underlying mail is identical.

What are the functions of email software?#

Whatever the type, email software exists to do a short list of jobs. A typical email client covers most of these. Server and marketing software handle a narrower set in more depth.

• Sending: composing a message, adding recipients and attachments, and handing it to an outgoing (SMTP) server for delivery.
• Receiving: fetching new mail from the server and showing it in your inbox, with notifications.
• Storing and syncing: keeping messages on the server and in sync across devices, plus a local copy for faster search and some offline reading.
• Organising: folders or labels, threads, flags, archiving, and rules or filters that sort mail automatically.
• Searching: finding a message by sender, subject, date, words in the body, or attachment.
• Filtering spam and threats: junk filtering, phishing warnings, and blocking remote images that track when you open a message.
• Contacts and calendar: an address book, plus handling meeting invites. Many clients bundle a full calendar.
• Managing several accounts: reading work and personal mailboxes in one app, sometimes in a single unified inbox.
• Security: signing in with OAuth or app passwords, encrypting connections with TLS, and optionally end-to-end encryption such as S/MIME or PGP.
• Automation and AI: templates, scheduled sending, reminders, and in newer clients, summaries, triage and drafted replies.

How does email software work?#

Email works because every piece of software speaks the same open standards. A client never sends mail straight to the person you are writing to. It hands the message to servers, and the servers pass it along. Here is the path one message takes.

1. 1

   You write the message in a client

   Outlook, Apple Mail, the Gmail app or a webmail tab builds the message: headers (From, To, Subject, Date) and a body, in the format defined by RFC 5322.

2. 2

   The client hands it to your outgoing server over SMTP

   SMTP (Simple Mail Transfer Protocol, RFC 5321) carries the message to your provider's outgoing server after you sign in.

3. 3

   Your provider's server finds the recipient's server

   It looks up the MX record for the recipient's domain in DNS and delivers the message there, again over SMTP. Authentication checks such as SPF, DKIM and DMARC happen at this step.

4. 4

   The recipient's server files it in their mailbox

   Spam and security filters run, then the message lands in the inbox, or the junk folder, on the recipient's provider.

5. 5

   The recipient's client fetches it over IMAP, POP3 or an API

   Their app connects to the mailbox and shows the new message. Most modern clients use IMAP; some talk to the provider's own API, such as the Gmail API or Microsoft Graph, instead.

IMAP vs POP3: why it still matters#

IMAP (RFC 9051, IMAP4rev2, which replaced RFC 3501 in 2021) leaves mail on the server and syncs its state everywhere. Read a message on your phone and it shows as read on your laptop. Archive it on the laptop and it leaves the inbox on the phone.

POP3 (RFC 1939) is older. It downloads messages to one device and is often set to delete them from the server afterwards, so mail read on one computer can vanish from every other device. It still has uses, such as keeping a full local copy, but for most people IMAP is the right choice.

POP is also being phased out in places. Google says Gmail on the web stops accepting new users of its POP-based "Check mail from other accounts" feature after Q1 2026, and existing users can keep it until January 2027. Third-party apps can still connect to Gmail over IMAP or POP.

Examples of email software#

These are the names you will see most often, grouped by job. Products change, so check each vendor's site for current features and prices. Details below are as of October 2026.

• Outlook: Microsoft's email client for Windows, Mac, iOS and Android, alongside outlook.com webmail. On Windows there are two versions, classic Outlook and new Outlook. Microsoft ended support for the old Windows Mail and Calendar apps on December 31, 2024, and points users to new Outlook.
• Apple Mail: the client built into macOS, iOS and iPadOS. It works with iCloud, Gmail, Outlook.com, Exchange and any IMAP account.
• Gmail: Google's webmail at gmail.com plus mobile apps, and the provider behind @gmail.com and Google Workspace addresses.
• Thunderbird: a free, open-source desktop client from the Mozilla family, popular with people who want local control and many accounts in one place.
• Mailchimp, Brevo, Klaviyo: email marketing software for newsletters and campaigns, not for reading your own inbox.
• Postfix, Dovecot, Exchange Server: server software that organisations run to handle their own mail.

Common misconceptions#

"My email app owns my address." It does not. Your provider does. Switch apps as often as you like and your messages stay on the provider's servers, ready for the next app to sync.

"Switching email clients means migrating my mail." With IMAP it rarely does. A new client signs in and syncs the same mailbox. The exceptions are things the old app kept only on your computer: local rules, local folders, signatures, or POP-downloaded mail.

"Email marketing software is just a bigger email client." It is a different tool. A client manages one person's conversations. Marketing software sends one message to a list, handles unsubscribes and tracks results. Using a normal mailbox for bulk sending tends to hit sending limits and spam filters.

Which kind of email software do you need?#

Start from the job, not the brand. Most people need only two pieces: a provider and a client.

Where AI Emaily fits#

Everything above describes the email client layer: software that syncs a mailbox over IMAP or a provider API and sends over SMTP. AI Emaily is an email client at that layer. It connects to the Gmail, Outlook, iCloud, Fastmail or IMAP account you already have, with no new address and no migration, and adds an AI layer on top: triage that sorts what each message needs, and drafts written from a Context brain and client profiles that you set up.

Nothing sends without your approval unless you choose more autonomy, and actions can be undone. It is not marketing or bulk-sending software. We build AI Emaily; the AI email assistant page shows what the AI layer does in practice.