What is an IMAP account?

In 2025 there were over 4.6 billion email users worldwide. The vast majority check their inbox on more than one device. You use your phone over breakfast, your laptop at work, and maybe a tablet on the couch. And you expect everything (every message, every folder) to look exactly the same on each one.

That’s what IMAP makes possible. It’s the protocol keeping your email synced across every device you use. In this guide, you’ll learn:

• What an IMAP account actually is and how it works
• How IMAP compares to POP3 and other protocols
• How to set up and troubleshoot IMAP, including with Mailfence

Here’s what you need to know.

What is IMAP?

IMAP stands for Internet Message Access Protocol. It’s the method your email app uses to read messages directly from your mail server.

Instead of downloading emails to one device, IMAP leaves them on the server. Your app simply displays what’s there.

This means you can open your inbox from any device and see the same messages, folders (depending on the client), and read/unread status.

Think of it like a shared bulletin board. Everyone looks at the same board, but nobody takes the notices home.

What is an IMAP account?

An IMAP account is simply an email account configured to use the IMAP protocol for retrieving messages.

When you add an email account to an app like Outlook or Thunderbird using IMAP settings, you’re creating an IMAP account.

Your emails live on the IMAP server. Your app connects to that server every time you check your inbox.

This is different from a POP3 account, which downloads emails and often removes them from the server entirely.

How does the IMAP protocol work?

The IMAP protocol follows a straightforward process. Here’s what happens each time you check your mail:

1. You open your email app. It connects to the IMAP server (usually over port 993 with SSL/TLS encryption).
2. The app requests your inbox. The server sends back a list of message headers (sender, subject, date).
3. You click on an email. The full message is fetched from the server and displayed.
4. You take an action (read, delete, move to a folder). That change is saved on the server.
5. You open another device. It connects to the same server and sees all your changes.

Every action syncs back to the server, which means your phone, laptop, and tablet always show the same thing.

What about instant delivery? How IMAP IDLE works

You might wonder why new emails appear almost instantly on your phone. That’s thanks to a feature called IMAP IDLE.

Instead of checking the server every few minutes (polling), IMAP IDLE keeps an open connection. The server pushes new messages to your app the moment they arrive.

IMAP IDLE is what makes your email feel real-time, and most modern IMAP servers and email clients support it by default.

IMAP vs POP3: what’s the difference?

These two protocols do the same basic job (fetching email) but they work very differently.

Feature	IMAP	POP3
Email storage	On the server	On your device
Multi-device sync	Yes	No
Offline access	Limited (unless cached)	Full (emails are downloaded)
Server space usage	Higher	Lower
Best for	Multiple devices	Single device

If you check email on more than one device, IMAP is almost always the better choice. According to a 2026 ZeroBounce survey, 64% of people now check email on their phones and tablets, making multi-device sync a practical necessity for most users.

POP3 can still make sense if you have limited server storage or prefer keeping all messages locally on one computer.

What is an IMAP server?

An IMAP server is the mail server that stores your messages and handles IMAP connections from your email apps.

Every email provider has its own IMAP server address. For example:

• Gmail: imap.gmail.com
• Outlook: outlook.office365.com
• Mailfence: imap.mailfence.com
• Yahoo: imap.mail.yahoo.com

You’ll need this server address when setting up your account manually in any email client.

Most IMAP servers use port 993 with SSL/TLS encryption, which protects your login credentials and email content during transfer.

What is an IMAP account password?

Your IMAP account password is usually just your regular email password, the same one you use to log in through a web browser.

However, some providers require an app-specific password instead.

If you’ve enabled two-factor authentication on Gmail or Outlook, for example, your normal password won’t work in a desktop email client. You’ll need to generate a separate app password.

Here’s where to find it:

• Gmail: Google Account → Security → App passwords
• Outlook: Microsoft Account → Security → App passwords
• Mailfence: Your regular Mailfence password works in most email clients. However, Mailfence also lets you generate service-specific passwords for added security, which is the recommended approach if you connect through third-party apps

If your email client keeps rejecting your credentials, an app-specific password is usually the fix.

How do I set up an IMAP account?

Setting up an IMAP account takes just a few minutes. The steps are similar across most email clients.

General setup steps

1. Open your email client (Outlook, Thunderbird, Apple Mail, etc.)
2. Choose “Add account” and select IMAP as the account type
3. Enter your email address and password
4. Fill in the IMAP server settings:
   • Incoming server: Your provider’s IMAP server address
   • Port: 993
   • Encryption: SSL/TLS
5. Enter outgoing (SMTP) server settings (your provider will list these too)
6. Test the connection and save

Most modern email clients detect IMAP settings automatically when you enter your email address. Manual setup is only needed if auto-detection fails.

Setting up Mailfence IMAP in Thunderbird (step by step)

Here’s a practical walkthrough using Thunderbird, one of the most popular free email clients:

1. Open Thunderbird and click File → New 

2. Click on Existing Mail Account

3. Enter your Mailfence display name, email address, and password.

4. Click Done.

Note: Use your primary Mailfence email address or username for authentication; alias addresses won’t work here. You can also find your exact connection details inside your Mailfence account under Settings → Account → My connection settings.

Mailfence supports IMAP on all paid plans, so you can access your secure, private email from any desktop or mobile client you prefer.

The same server credentials work in Outlook, Apple Mail, or any other standard email app. Just plug them into the IMAP and SMTP fields.

Troubleshooting common IMAP problems

IMAP is reliable, but things can occasionally go wrong. Here are the most common issues, including a few fixes other guides don’t mention.

“Cannot connect to server”

Double-check your IMAP server address and port number. A single typo will block the connection entirely.

Also confirm that SSL/TLS is selected. Most servers reject unencrypted connections on port 993.

If everything looks correct, check your firewall or antivirus software. Some security tools block port 993 by default. Temporarily disabling them can help isolate the problem.

“Authentication failed”

This usually means your password is wrong, or your provider requires an app-specific password.

If you’ve recently enabled two-factor authentication, generate a new app password and use that instead.

Also make sure you’re entering your full email address as the username, not just the part before the @ symbol.

Emails not syncing across devices

Make sure all your devices are configured as IMAP, not POP3. If even one device uses POP3, it may download and remove messages from the server, breaking sync for everything else.

Check each device’s account settings to confirm the protocol type.

Mailbox is full

Since IMAP stores everything on the server, your mailbox can fill up over time.

Delete old emails or archive them locally to free up space. Most providers show your storage usage in account settings.

Slow loading

IMAP fetches messages on demand, so a slow internet connection means slow email.

Try enabling offline or cached mode in your email client. This stores recent messages locally so they load instantly, even when your connection is sluggish.

Some ISPs also throttle IMAP connections, especially on mobile networks. Switching between Wi-Fi and mobile data can sometimes fix unexplained slowness.

Keep your IMAP email private, not just synced

Here’s something worth understanding: IMAP encrypts the connection between your app and the server, but it doesn’t encrypt the emails themselves.

Your messages still sit on the server in readable form. That means your email provider (or anyone who breaches the server) could potentially access them.

This matters more than ever. Over 75% of targeted cyberattacks start with an email, and the global email encryption market is projected to grow from $9.3 billion in 2025 to over $23 billion by 2030 – a sign that businesses and individuals are taking email privacy increasingly seriously.

That’s where end-to-end encryption matters. It scrambles the actual content of your messages so only you and the person you’re writing to can read them – your provider can’t, and neither can anyone who intercepts the message.

Mailfence gives you IMAP access alongside built-in end-to-end encryption, digital signatures, and Mailfence’s Productivity Suite, all backed by Belgian privacy laws and GDPR protections.

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