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POP3 vs. IMAP: Definitions and key differences

POP3 and IMAP are two of the most common protocols for sending and receiving emails. While POP3 downloads emails to the user’s device, IMAP keeps them on the mail server. Let’s find out how these protocols work and their key differences to help you decide which one’s right for you.

POP3 vs. IMAP: Definitions and key differences

What is POP3?

POP3 is the third version of the Post Office Protocol — an email protocol that automatically downloads messages from the mail server to the user’s device. Email providers that support POP3 allow users to open and read their emails later (even without an internet connection).

Users don’t have to open the email client app to download emails — POP3 does it for them in the background. The emails are typically deleted from the server and stored on your device instead, so you may be unable to access them on other devices.

POP3 is considered a simple and user-friendly way to access your mailbox because the email messages and attachments have already been downloaded. It’s much quicker than having to wait for them to download as you’re trying to open them.

However, like most email protocols, POP3 has its downsides. Because it downloads emails and attachments automatically, it may download attachments that contain malware or viruses. Not all email attachments are safe — and POP3 doesn’t have a native way of identifying whether they are.

How does it work?

Here’s a more detailed explanation of how POP3 works:

  1. First, you configure your email client (e.g., Outlook) with your email address and the POP3 server settings.
  2. When you open your email client on your phone or another device, it connects to the POP3 server where your emails are stored.
  3. You enter your email and password to prove you have permission to access this account.
  4. Once authenticated, POP3 automatically collects all the new emails waiting on the server and downloads them to your device (including attachments).
  5. The downloaded messages are stored on your computer or smartphone, so you can read and manage them even if you disconnect from the internet.
  6. The messages POP3 downloads are deleted from the email server by default — but you can choose to leave a copy on the server if you want to be able to access your emails on several devices.

Advantages of POP3

  • pros
    Emails are downloaded to your device, which is great if you have limited server storage space.
  • pros
    Easy to open attachments because they’re already downloaded.
  • pros
    You can access emails even without a reliable internet connection.
  • pros
    Relatively easy to set up and straightforward to use.

Disadvantages of POP3

  • cons
    You can’t check whether an attachment is safe before downloading.
  • cons
    If your device breaks, you may lose your emails and attachments (unless they’re backed up).
  • cons
    Email folders may take up much of your device’s storage space.

What is IMAP?

IMAP (or the Internet Message Access Protocol) is an email protocol that stores your emails on the server, allowing you to access them on various devices simultaneously. Unlike POP3, which downloads emails from the mail server, IMAP functions as an intermediary between email servers and email apps.

With POP3, accessing your email messages offline is easy — it’s one of the main features of this email protocol. While IMAP doesn’t automatically download every email to your device for offline access, it is possible to download the email’s content once you’ve opened it. Let’s dig into how IMAP works.

How does it work?

Unlike the Post Office Protocol, the Internet Message Access Protocol keeps your emails on the email server, letting you access them from any device.

  1. When someone sends you an email, it arrives and is stored in your email server’s inbox.
  2. Your email app downloads a temporary version of your email’s metadata (i.e., date, sender, and subject).
  3. Any files attached to the email remain on the email server and can be accessed from multiple devices.
  4. When you open the email, IMAP downloads the content — but you choose whether you want to download the attachment (it doesn’t happen automatically).
  5. Any changes you make — like deleting, opening, or replying to emails — are reflected on the server. For example, if you open your mailbox on your computer, you will see the emails you’ve already read and replied to on your phone.

Advantages of IMAP

  • pros
    Uses less storage space on your device because all emails are stored on the mail servers.
  • pros
    If your device breaks, your emails are safe because they’re stored on the server.
  • pros
    You can access your emails on multiple devices because they’re constantly synchronized.

Disadvantages of IMAP

  • cons
    Emails won’t work without an active internet connection.
  • cons
    Reading emails is slower than POP3 because all folders are synced whenever you send or receive a new message.
  • cons
    If you get a lot of emails, you may need to purchase more mailbox storage space.
  • cons
    IMAP can be complex to set up for some users, especially when it comes to organizing and managing folders and emails.

POP3 vs. IMAP: What’s the difference?

Now that we know how each email protocol works, let’s review the main differences between IMAP and POP3. The table below will help you quickly compare IMAP vs. POP3 to understand which protocol works best for how you use email.

Email retrievalDownloads emails to the email client (e.g., app) and deletes them from the server.Keeps your emails on the email server, synchronizing them across devices.
Multiple devicesLess suitable for multi-device access.Great for multi-device access.
Email storageStores your emails on your device’s hard drive (i.e., local storage).Offers server-based storage, keeping your emails and folders on the email server.
Offline accessAllows you to access your emails offline after the initial automatic download.You can access emails you’ve previously opened offline, including attachments.
Real-time syncDoesn’t sync email messages across devices.IMAP supports real-time synchronization, reflecting all new emails and changes to emails on all devices.
AttachmentsAutomatically downloaded with emails.Stored on the server and can be downloaded to the device manually.
SecurityLacks strong security measures (encryption may be available but not offered by default).Supports stronger security measures like encryption, 2FA, and server-based storage for backups.

When choosing between IMAP and POP3, it’s important to consider your specific needs and preferences. While being able to access emails on multiple devices may be important to some people, others may want to store all their email messages on one device.

What do these email protocols mean in real life?

Learning how IMAP and POP3 work is important because it tells you about each protocol’s pros and cons. You can uncover their shortcomings — like the fact that POP3 automatically downloads attachments or that IMAP requires a stable internet connection — and make an informed decision.

While most email providers will automatically assign you the protocol they use by default, it is in your power to choose which email client you want to use based on the protocols they support.

Now that you know the key differences between POP3 and IMAP, you may even want to get an email account with a different provider to take advantage of a specific protocol’s benefits.

Most email providers support both POP3 and IMAP. When you attempt to create an account with a new provider, it’ll most likely set it up with IMAP. However, if you decide that POP3 is a better protocol for you (maybe because you only plan on reading emails on one device and want to read your emails offline), you may investigate whether the provider also supports POP.

For example, when adding email accounts to Outlook, Thunderbird, or Apple Mail, these providers usually attempt to set you up with IMAP. If you’re having trouble setting it up, it could be because the email account you’re trying to add is set up for POP access.

In this case, you’ll need to check your email provider’s documentation or contact their support to find out the name of the POP server. Once you know the name, you’ll need to enter it into the email client app to set it up.