POP3 vs IMAP vs Exchange ActiveSync. What’s the difference?

In this blog post, we compare POP3 vs IMAP vs Exchange ActiveSync. How do these protocols work? What are their pros and cons? We will conclude by giving tips on how to use them with your Mailfence account.

Quick recap: which protocol should you choose?

If you are short on time, here is the one-line version for each protocol. The rest of the article explains the reasoning.

• POP3: downloads mail to one device and can remove it from the server. Best if you read email from a single computer and like keeping messages offline.
• IMAP: keeps mail on the server and mirrors the same folders on every device. Best if you check email from a phone, tablet and computer and want them all in sync.
• Exchange ActiveSync (EAS): syncs email, contacts and calendars together on mobile devices. Best if you want everything in one place and prefer not to configure sending separately.

Post Office Protocol (POP3)

In POP3, the mail server receives all the emails sent and stores them accordingly in your mailbox.

POP3 offers a simple way to download your emails from the remote mailbox Inbox to your local mailbox. That’s because POP3 downloads only the content of your Inbox, not that of other folders.

The POP3 client software connects to an email server and fetches all the newly received messages (the ones not already downloaded) present in the Inbox. Then, depending on user specifications, the original emails are deleted from the server or not, so emails can either be moved or just copied.

Note: sending email is quite different from receiving email. For example, when sending an email from a computer, sent emails are only stored on the computer you are sending from and cannot be viewed in the ‘Sent items’ folder of other devices.

Pros:

• POP3 is most useful if you only check email from one device.
• Users can enjoy the comfort of reading and organizing their emails offline.
• It helps users who prefer to store their emails on their local devices rather than on a remote server for privacy reasons instead.

Cons:

• No sync between devices. If several devices fetch the same mailbox over POP3 without deleting messages, each device ends up with its own separate copy.
• Actions do not carry across. Anything you do to a message (deleting it, filing it in a folder, tagging it) applies only on the device where you did it. This makes managing mail across devices more cumbersome.
• Delete-on-download locks other devices out. If you set your POP3 client to remove messages from the server after downloading, your other devices can no longer fetch them. That removes the convenience of checking email from more than one place.
• Inbox only. POP3 downloads the content of your Inbox and nothing from your other folders.

Internet Message Access Protocol (IMAP)

With IMAP, the mail server receives and stores in your mailbox all the emails that you receive.

IMAP offers a simple way to read emails stored in a remote mailbox.

The messages remain stored on the remote server, and an IMAP client allows you to read and manipulate them (delete, move, …). In simple words, IMAP provides a synced view of a remote mailbox on any device.

For a complete walkthrough, including step-by-step setup instructions for Thunderbird and other clients, see our guide on what an IMAP account is and how to set one up.

Pros:

• Access from any device. You can read and manage your mail from your computer, phone and tablet, and they all stay in step. This suits people used to checking email across several always-connected devices.
• The same view everywhere. The server is the single source of truth that every IMAP client syncs with, so your folders and tags look the same in each one. IMAP gives you access to your whole folder hierarchy, not just the Inbox.
• Deletion is handled server-side. When you delete a message in the client, it is not always removed from the server straight away. The client marks the message as deleted (this marker is called a ‘flag’), and the server then acts on it according to your settings, for example moving it to Trash or removing it immediately.

Cons:

• You are limited by your mailbox size. Because your email stays on the server, you are bound by the storage limit of your plan. You can work around this by making local archives.
• Phones may not download everything. On most smartphones, IMAP clients try to save data by keeping only the most recent messages available offline. You can change this in the client’s settings to allow a full download with offline access to every message.
• Server storage may not suit everyone. For security and privacy reasons, some people would still rather keep their mail on their own device than on a remote server.

Exchange ActiveSync (EAS)

Simply put, Exchange ActiveSync protocol allows your device to synchronize emails, calendars, and contacts with a messaging server.

Exchange ActiveSync is a Microsoft’s proprietary protocol. However it was subsequently ‘licensed’ to other companies and has become a kind of standard for synchronization between groupware and mobile devices.

Pros:

• Email, contacts and calendar together. EAS syncs your contacts and calendar alongside your email on mobile devices. This is the main advantage over IMAP and POP3, which only handle email.
• Sending is built in. EAS also sends email, so you do not need to configure sending separately. (Setting up plain SMTP for sending can be fiddly, but that is a topic for another blog post.)
• Access from any device. Your email stays on a remote server, so you can reach it from any device without losing your folders and tags. Many mail clients, including the default Android and iPhone apps, work with EAS out of the box.

Cons:

• Limited offline reading. A device only syncs the most recent messages (commonly the last few weeks up to a month or so, depending on the sync window you set), so older mail may not be available offline.
• Server storage may not suit everyone. As with IMAP, some people prefer to keep their data on their own device for security and privacy reasons rather than hosting it on a remote server.

Which protocol should I use: POP3 vs IMAP vs Exchange ActiveSync?

So which email protocol should you use?

POP3 vs IMAP vs Exchange ActiveSync?

Depending on your personal requirements and preferences, you can narrow down your choice:

• If you only need to access your Inbox from a limited number of devices, POP3 is a suitable choice. Sending emails still requires separate configuration of SMTP services.
• If you need to access your full mailbox (i.e. all your folders, or just a part of them) and access them from many devices, IMAP is the right choice. Here also, sending emails still requires separate configuration of SMTP services.
• If you need full access to your mailbox, contacts, and events, ActiveSync is the right choice. It also allows us to send emails without additional configuration.

At a glance

Mailfence supports all three options. Being able to use these protocols is one of the many reasons to upgrade to a paid account.

Looking for a way to set up your account with these protocols? Have a look at our dedicated article.

Also, feel free to follow our Email security and privacy awareness course to protect yourself against today’s dominant cyber threats.

FAQ about POP3 vs IMAP vs Exchange ActiveSync