What is the Difference Between POP3 and IMAP?

On May 27, 2020
4min read
Piotr Malek Technical Content Writer @ Mailtrap

Retrieving your emails is a serious business. And a serious business requires a conscious decision about which method to use. Luckily, there are usually just two options to choose from, and they’re quite different from each other. So let’s get to the point—IMAP vs. POP3. Which one should you choose?


POP3 is the older and the simpler of the two protocols. The name stands for Post Office Protocol and, to no surprise, POP3 is its third revision. It’s been around since 1985, enduring various updates ever since. It is still in use (though it’s not as popular as it used to be). POP4 has appeared in the meantime, but only as a small extension to POP. It hasn’t moved forward since 2003. Names POP and POP3 are used interchangeably.

When POP3 is implemented to retrieve emails from a server, the following flow happens:

  • The connection is established between a client and a mail server.
  • An email client downloads all the emails from a server, along with attachments.
  • They’re saved on a device that initiated the connection.
  • Emails are then deleted from a mail server (by default*).
  • The transmission ends.

* Most clients can be configured to keep a copy of downloaded emails on a server, either for a specific time (e.g. 7 days) or permanently.

POP3 doesn’t allow a user to preview emails on a server, search through them, delete or organize them into folders. It does precisely what it was created for: it fetches emails from a server and, most often, deletes them right after.

POP3 can initiate secure SSL/TLS transmission, known as POP3DS. It’s configured to listen on port 110 (plain-text transmission) and 995 (with SSL/TLS enabled).


IMAP is the second of the major protocols for retrieving emails. It’s a younger one, but certainly can’t be called a very recent innovation. It was originally developed in 1986, with the latest, fourth revision dating back to the early ‘90s. Similar to the other protocol, the name IMAP is used interchangeably with IMAP4, although the former is more common.

IMAP works in the following fashion:

  • The connection is established between a client and a mail server.
  • The requested content is fetched and cached on a device (e.g. a list of new emails with the headers and, sometimes, pre-headers).
  • User-initiated actions are performed—messages are deleted, archived, marked as read, etc.).
  • The transmission ends.

Note that with this method, emails are not fetched from a server. They will only be retrieved when a user chooses to open them on any device. And even then, only a copy of an original message will be rendered, the original piece being safely stored on a server.

IMAP also offers support for SSL/TLS transmission (it’s known as IMAPS). IMAP listens on ports 143 (plain-text) and 993 (SSL/TLS).

What are the differences between POP3 and IMAP?

There are many differences between typical POP3 and IMAP implementations:

Emails are downloaded to a local deviceEmails are kept on a server (they’re only synchronized)
Changes made to emails are not reflected on other devicesAny changes are synchronized across devices (e.g. a message marked as read)
Emails can only be accessed from one device at the timeThere’s no limit on the number of devices accessing emails simultaneously
A user needs to download an email to read itHeaders of an email can be read without downloading the rest of the content
If emails are downloaded beforehand, no internet connection is needed to read themInternet connection is necessary to view the entire contents of an email
Users can’t organize emails on a server (group them into folders, delete them, etc.)Users can freely organize emails on a server
POP3 is more simple and as such, faster to set up and implementations are less error-proneIMAP is more complex to implement and the risk of faulty installation is higher

IMAP vs POP3 – Which protocol should you choose?

If you’re still wondering whether you should choose IMAP4 or POP3, here are a few instances in which either option will work.

Pick IMAP if:

  • You’re planning to sync email across different devices (computers, mobile devices, wearables, etc.)
  • You have a stable internet connection and can sync messages whenever you need to read them
  • You have sufficient storage space on a server to store your emails (or are okay with regularly deleting some)
  • You’re worried about potential data loss and need to have a backup in the cloud

Pick POP3 if:

  • You have a limited internet connection and fetching emails all at once is a more viable option
  • You’re the only user of a mailbox and use a single device to fetch messages
  • You receive a large volume of emails and are worried about the storage space in the cloud (in such cases, storing emails locally may be more feasible)

For the majority of users, IMAP is a better option. POP3 was a fantastic option back when a stable internet connection was a luxury. Back then, connecting one, fetching all emails, and quickly terminating a connection was cost-effective and allowed for quick access to all emails.

These days, we rarely use just one device to fetch emails. Mobile and Wi-Fi networks have also become omnipresent and many of us have no issues with fetching emails on the go. Syncing them across devices and automatically backing them up are additional benefits we can’t opt for with POP3 in place.

IMAP is the default protocol for receiving email in most modern email clients. Many of them, including popular ones like Gmail or Yahoo!, offer support for both protocols. So the choice is really up to you!

Wrapping up

Up for some more reads? Our article on SMTP Security offers insights on various threats that every serious email sender needs to be aware of, along with tips for securing your transmissions. If you’re curious about which ports work best for email sending and receiving, we’ve got this covered for you in our post on SMTP Ports.

And while we’re at it—how do you test your emails before they’re sent to real users? Over half a million devs and QAs use Mailtrap to do so.

Mailtrap is used to capture your test emails in a safe pre-production environment. You can then preview them, inspect them for HTML/CSS errors, check spam scores, and forward them to teammates or clients. Check out our 1-minute demo.

Article by Piotr Malek Technical Content Writer @ Mailtrap