It’s an everyday routine: you open up your email and see messages pop into your inbox. But behind the scenes, email protocols are hard at work. These are the technical procedures that define how your mail is stored, accessed and managed, with two of the most popular options being POP3 and IMAP.

Email is transported across the internet by mail servers, which receive and deliver messages from email client software like Outlook and Thunderbird, as well as browser-based webmail applications such as Gmail. Most email clients can be configured to use POP3 or IMAP to access and display mail.

But if you have the choice of either POP3 or IMAP, which one should you go for?

How POP3 email works

POP3 (Post Office Protocol version 3) works by establishing a connection between the email client and the POP3 mail server, then downloading messages to the client computer, before terminating the connection.

Typically, the downloaded emails are deleted from the server when this happens, and from then on are only stored locally on the client device (although POP3 can be configured to keep copies on the server).

Only one computer or device can connect to a POP3 mailbox at a time, and emails are usually only downloaded to a single client. Because mail is stored locally after it’s been retrieved from the server, it can be viewed and edited offline, without requiring a permanent internet connection.

What is IMAP email?

IMAP (Internet Message Access Protocol) also establishes a connection between the mail server and client, but unlike POP3, it maintains this connection throughout the user’s session, not just when emails are retrieved.

With IMAP, all messages stay saved on the server after retrieval by the client, until the user decides to manually delete them.

This means that multiple computers or devices can connect to the same IMAP mailbox, and all have the same access to the same messages on the server, as long as an internet connection is available.

POP3 or IMAP: making your choice

POP3 makes sense for individuals who access their email from a single machine, with the added bonus of not needing a constant internet connection to access messages once they’ve been retrieved from the server.

POP3 is the simpler of the two protocols, and because POP3 routinely deletes mail from the server, it’s generally less of a burden on server resources.

Even so, with storage relatively cheap and emails taking up relatively little space, there’s no real barrier to choosing IMAP over POP3.

IMAP is better for users on multiple devices who need an equal level of access on their smartphone, tablet and PC. IMAP also offers more complex features than POP3, such as advanced options for managing folders and status flagging of emails.

However, it’s worth noting that IMAP does not store email locally by default. Some clients will keep a few weeks’ worth of mail to be accessed offline, but these will be stripped of any images and attachments. With IMAP, there’s the risk of being stuck without a connection and no way to access previously retrieved emails.

But in our increasingly ‘always online’ personal and professional lives, relying on multiple devices on a daily basis, IMAP is generally regarded as the more relevant mail protocol. Connectivity is always improving, and the benefits of cloud computing mean that users can generally rely on enough online storage.

Email protocols: a final comparison

A quick summary of the key differences between POP3 and IMAP:


  • Connection when retrieving emails only
  • Emails are usually deleted from the server after retrieval
  • Email retrieval only possible via individual clients


  • Permanent connection
  • Emails stay on the server until manually deleted
  • Email retrieval possible via multiple clients

Ultimately, your choice of either POP3 or IMAP will come down to how you manage your mail. Do you need to access the same emails on your office desktop and your laptop on the road? IMAP is the way to go. If however you view all your emails on a single computer, and want your messages to be always locally stored, POP3 might be the better option.

If you’re still not sure, the good news is that it’s relatively simple to switch between POP3 and IMAP on most email clients.

At Fasthosts, we offer a full range of email hosting services with support for both POP3 and IMAP. So whichever email protocol you settle on, you can take advantage of business-class features, flexibility and security, plus outstanding 24/7 technical support.