The Differences Between POP3 And IMAP

It’s easy to forget just how much of a revelation email really was when it first debuted. The first in-house email systems began to emerge in the late 1970s, and by the mid-80s, LAN systems had become popular, leading to the widespread debut of three email systems in the 1990s: SMTP, IMAP, and POP3. These three protocols dictate how email works, and you’ve probably heard of at least two of them before.

Today, we’re going to be directly comparing POP3 and IMAP and figuring out exactly what the differences between them are. This isn’t really a typical POP vs. IMAP debate; they’re both used for different things and can’t really go “head-to-head”, as it were. Still, if you’re a developer – or just a hobbyist looking to understand the tech better – it’s crucial to understand exactly what the differences are. Here’s our look at POP3 and IMAP and where their key differences lie!

What is POP3?

Let’s begin with a quick rundown of what POP3 is. POP stands for Post Office Protocol, and in essence, it’s a protocol for sending and receiving emails, just like IMAP. However, POP3 doesn’t rely on a central server as much; it involves a client getting emails transferred from the server, meaning that it’s possible to read emails offline if you’re using POP3. 

Basically speaking, POP3 works when a client connects to a POP3 server, then tells the server to download email messages. Those messages are then stored locally, while the server copies are deleted. This is essentially a one-way transaction in which there’s no real synchronisation between devices; instead, the client machine is downloading emails from the server, allowing them to be read by those who are using the client computer.

What is IMAP?

Conversely, IMAP – which stands for Internet Message Access Protocol – works in a more synchronised way. Just like POP3, IMAP connects to a server and asks it if any new messages have been received, but unlike POP3, IMAP doesn’t download emails to the local machine. 

Instead of doing this, IMAP downloads email content when you open a message, and when the change from unread to read – or a modification like deletion – is detected, the server copy of the email is also updated to reflect this change. This means that local and server copies of emails are consistent when it comes to IMAP. It’s possible to set up accounts with many modern email clients and then use either IMAP or POP3 protocols depending on your preference.

What are the advantages of POP3?

Although it might sound like a slower and less technologically advanced protocol, POP3 does actually come with its own set of advantages. Here are a few reasons you might want to use POP3.

  • It lets you store local email copies. When you’re using POP3, emails are downloaded to a local machine, which means they can easily be checked even if you don’t currently have an internet connection. This is ideal if you’re in a setting where the internet is spotty or inaccessible, or you know you’re going to be without a connection for a protracted period of time.
  • Server space is saved. You won’t have to use as much server space with POP3, because you’ll be storing emails on a local machine, so a server won’t have to bear the brunt of a huge amount of emails.
  • Opening attachments is quick and easy. All attachments with POP3 will be stored on your machine, so it’ll be easy to quickly access attachments, even if they’re large. By contrast, IMAP can sometimes be difficult when it comes to attachments, because you’re retrieving copies of the files from the server.

What are the disadvantages of POP3?

Of course, POP3 also comes with disadvantages. Here are some of the reasons that you might want to stay away from POP3, or some of the use cases where it might not come in handy.

  • You could lose emails. Since email copies are only stored on a local machine with POP3, you might lose emails if your file system fails or your drive becomes corrupted. It’s important to make regular backups, but it’s also easy to forget to do so.
  • Viruses can infect files. Server-side files tend to have better virus protection because they’re not just sitting on your machine, but POP3 means that since all emails are local, a virus could have an easier time snaking its way into your file system without proper protection.

What are the advantages of IMAP?

Naturally, IMAP comes with its own set of advantages as well, and they should be fairly obvious based on what the advantages of POP3 look like. Here are a few of them.

  • Messages can be accessed by lots of different machines and clients. Emails are synced to a server with IMAP, so you can access the same message on your phone as you would on your desktop and the message will appear pretty much identical.
  • You won’t lose emails as easily. Since emails are stored on a central server, you won’t lose them, even if you’ve downloaded a local backup and your hard drive fails. You’ll still have the server-side backup to rely on.
  • You can use desktop apps or webmail. Whether you’re accessing your emails from a browser or from a dedicated desktop client, you’ll still get the same messages, because they’re all synchronised with a server.

What are the disadvantages of IMAP?

Sadly, it’s not all fun and games with IMAP either; you’ll find there are a host of unique disadvantages to this protocol. Here are some of the drawbacks to IMAP.

  • You need a robust internet connection. Although many modern IMAP services don’t require a great connection to use, attachment-heavy messages or longer emails might need a good internet connection to read, and if you don’t have a good connection, you may struggle to access your email.
  • Losing your emails is out of your hands. If you don’t make regular local backups, then your emails could vanish in the event of a major server failure, and that’s completely out of your hands; the server is run by someone else, so the fate of your server-side emails is left up to that company or entity.