Smart. Focused. Email.
Fast, cross-platform email designed to filter out the noise - so you can focus on what's important.
Definition
💡 IMAP: Internet Message Access Protocol, the standard way email clients retrieve messages from mail servers. IMAP is defined by RFC 9051 and was designed with the goal of permitting complete management of an email box by multiple email clients. Unlike POP3, which downloads emails to your device, IMAP keeps everything on the server.
Why IMAP matters
A key feature of IMAP is that it allows users to access their emails from any device, acting as an intermediary between email servers and email clients rather than downloading emails from the server onto the email client. That means you can check email on your phone, switch to your laptop, then check again on your tablet, and everything stays synced. Read an email on one device? It shows as read everywhere. Delete something? Gone from all your devices. Move a message to a folder? That change happens across the board.
IMAP was created by Mark Crispin in 1986 as an alternative to Post Office Protocol (POP), which was used to download messages from the email server to the local device.
The big difference is where your emails live. Unlike POP, IMAP stores your messages and folder structure on the mail server, working similarly to cloud email. Virtually all modern email clients and servers support IMAP, which along with the earlier POP3 are the two most prevalent standard protocols for email retrieval. Gmail, Outlook, Yahoo Mail all use IMAP. It's the default these days.
How IMAP works
IMAP runs on a client-server model. Your email app (the client) talks to the mail server using specific commands.
An IMAP server typically listens on port number 143, while IMAP over SSL/TLS (IMAPS) is assigned the port number 993. Port 143 is unencrypted and shouldn't be exposed to the internet. Port 993 adds TLS encryption, which is what you should actually use.
Here's the basic flow: An email client connects to the server via IMAP when a user signs in, using specific ports for establishing the connection. You authenticate with your username and password. Then the client can start sending commands—SELECT to open your inbox, FETCH to retrieve specific messages, SEARCH to find emails matching certain criteria.
The clever part is that the email client displays only the headers of each email initially, and messages and attachments are downloaded to the client only when the user taps on them. You're not downloading your entire mailbox every time you open your email app. Just the headers, which makes the process much faster.
Clients often stay connected as long as the user interface is active and download message content on demand. Your email app maintains an open connection to the server and gets notified when new mail arrives. That's how you get instant notifications.
IMAP vs POP3
The choice basically comes down to where you want your emails stored.
IMAP keeps emails on the server. With IMAP, emails are kept on the server until you delete them, providing flexibility and peace of mind—you know you'll always have a copy even if your device malfunctions. Everything syncs across devices. You can organize emails into folders on the server, and those folders appear everywhere.
POP3 downloads emails to your device. POP3 works by retrieving emails and files directly from your email server and downloading them to your device, which means that once an email has been downloaded, it typically gets removed from the server. You can only access those emails from that specific device. No syncing, no multi-device access.
IMAP is often recommended for modern email usage, particularly when you need to check emails from multiple devices. Unless you only ever use one computer and want offline access to all your mail, IMAP is the better choice.
The trade-off? IMAP requires far more server-side resources, incurring a significantly higher cost per mailbox. But for users, that doesn't matter. Your email provider handles it.
Setting up IMAP
Most email apps auto-detect IMAP settings when you add an account. But if you need to configure it manually, for example, if automatic setup fails or when you’re using a custom, work, or less common email provider that isn’t recognized by the app, you can try the following:
Incoming server (IMAP): Your email provider's IMAP server address. For Gmail, it's imap.gmail.com. For Outlook, imap-mail.outlook.com. Check your provider's documentation.
Port: 993 for encrypted IMAP (IMAPS), which is what you should use. Port 143 is unencrypted and insecure.
Security: SSL/TLS encryption. Don't use unencrypted connections.
Outgoing server (SMTP): IMAP only handles receiving email. You still need SMTP for sending.
Spark works with Gmail, iCloud, Yahoo, Exchange, Outlook, Kerio Connect, and other IMAP/EWS email accounts. The app detects the right settings and connects securely without manual configuration. If Spark can’t detect them automatically, the window for adding Additional Settings will appear.
Using IMAP securely
Always use encryption. One of the biggest security issues with IMAP is that it transmits logins from the client to the server in plain text by default, meaning usernames and passwords are not encrypted. Configure IMAP over TLS (port 993) to protect your credentials.
Manage server storage. Since IMAP keeps everything on the server, your mailbox can grow indefinitely. Delete old emails you don't need, archive important ones locally if you're running out of space.
Use app-specific passwords. IMAP is not inherently compatible with multi-factor authentication (MFA), which can be exploited to bypass MFA requirements. Most email providers let you generate app-specific passwords that work with IMAP while keeping your main account protected by MFA.
Keep your client updated. Security vulnerabilities get patched regularly. An outdated email client is a security risk.
Don't leave port 143 open. Port 143 should not be open and accessible to the outside world because it is not secure, and criminals can take advantage of it and initiate different attacks. Always use encrypted connections on port 993.
Related content
Related terms