Email protocols are essential for how we access, store, and manage our emails, but many users aren’t aware of how they work. In this article, we’ll dive deep into two of the most popular email protocols—POP3 and IMAP. You’ll learn about their differences, how each one works, and which is the best choice for your needs. Whether you’re an email user curious about how your inbox is managed, a business looking to optimize email setup across multiple devices, or involved in email marketing, this guide will help you make the right decision.
Table of Contents
What Are Email Protocols and Why Do They Matter?
Email protocols like POP3 and IMAP determine how your email client (such as Outlook or Apple Mail) interacts with your email server. These protocols allow you to retrieve email from the server and access it on your device. Understanding how each protocol works can help you choose the best setup for how you want to access and manage your emails.
See also: Constant Contact vs Mailchimp.
What Is POP3? The Post Office Protocol Explained
POP3, or Post Office Protocol version 3, is one of the oldest and most widely used email protocols. When you use POP3, it downloads your email from the mail server onto your device, removing it from the server. Once the email is downloaded, it’s stored locally, meaning you can access your email even when you’re offline. However, since the email is deleted from the server, you won’t be able to access it on other devices unless you’ve set your client to leave a copy on the server.
Further reading: HubSpot vs Mailchimp.
What Is IMAP? The Internet Message Access Protocol Explained
IMAP, or Internet Message Access Protocol, is a more modern protocol that allows you to access your emails from multiple devices. Unlike POP3, when you use IMAP, your emails remain stored on the server and are only downloaded temporarily when you access your inbox. This setup means your emails and folders are synced across multiple devices, making it an ideal choice for users who want flexibility. Both protocols only control how messages reach your email client; they don’t change your address or domain (for that distinction, see email domain vs email address).
POP3 vs. IMAP: What Are the Key Differences?
The most significant difference between POP3 and IMAP is how they handle emails. With POP3, emails are downloaded and deleted from the server, while IMAP keeps your emails stored on the server, allowing you to access them from multiple devices. If you prioritize offline access and don’t need to send email or access webmail from different devices, POP3 may be a better choice. However, if you often use email across multiple devices like your phone, computer, and tablet, and want to sync effortlessly while sending emails via SMTP, IMAP is the preferred option.
| Feature | POP3 | IMAP |
|---|---|---|
| Where email is stored | Downloaded to one device; usually removed from the server | Kept on the server; devices show a synced copy |
| Multiple devices | Possible, but each device downloads its own copy and nothing syncs | Built for it: phone, laptop and webmail all show the same inbox |
| What syncs | Nothing. Read status, folders and deletions stay on one device | Read and unread status, folders, flags, deletions and sent mail |
| Offline access | Full offline access to everything downloaded | Recent or cached mail only, unless you set the client to download everything |
| Server storage used | Low, since mail is removed after download | High, since everything stays until you delete it |
| Device storage used | High, since every message lives locally | Low to medium, depending on how much the client caches |
| If your device fails | Mail is lost unless you have a backup | Nothing is lost; sign in on a new device |
| Default port (STARTTLS or unencrypted) | 110 | 143 |
| Secure port (SSL/TLS) | 995 | 993 |
| Best for | One computer, limited server space, offline archives | Anyone who checks email on more than one device (most people today) |
POP3 and IMAP Port Numbers
A port is the numbered “door” your email client uses to reach the mail server. POP3 and IMAP each have two standard ports: one for connections that start unencrypted and can upgrade with STARTTLS, and one for connections that are encrypted with SSL/TLS from the first byte. Outgoing mail always goes through SMTP, whichever of the two you use for incoming mail.
| Protocol | What it does | Unencrypted / STARTTLS port | SSL/TLS port |
|---|---|---|---|
| POP3 | Downloads incoming mail | 110 | 995 |
| IMAP | Syncs incoming mail with the server | 143 | 993 |
| SMTP (submission) | Sends outgoing mail from your client | 587 (STARTTLS) | 465 |
| SMTP (relay) | Moves mail between mail servers | 25 (STARTTLS when supported) | None. Not for email clients |
Which port should you use?
- IMAP: use 993. It encrypts the connection from the start. Use 143 only if your provider tells you to, and only with STARTTLS turned on.
- POP3: use 995 for the same reason. Port 110 is the older, unencrypted default.
- Outgoing mail (SMTP): use 465 or 587, whichever your provider lists. Never use 25 in an email client; many internet providers block it to stop spam.
- If your app asks for “SSL/TLS”, pick 993, 995 or 465. If it asks for “STARTTLS”, pick 143, 110 or 587.
The current standard for email encryption, RFC 8314, recommends the SSL/TLS ports (993, 995 and 465) over STARTTLS because the connection is never unencrypted, even for a moment. For more on how this works, see our guide to SSL email.
POP3, IMAP and SMTP settings for Gmail, Outlook and Yahoo
| Provider | IMAP server (port) | POP3 server (port) | SMTP server (port) |
|---|---|---|---|
| Gmail | imap.gmail.com (993, SSL) | pop.gmail.com (995, SSL) | smtp.gmail.com (465 SSL or 587 STARTTLS) |
| Outlook.com | outlook.office365.com (993, SSL/TLS) | outlook.office365.com (995, SSL/TLS) | smtp-mail.outlook.com (587, STARTTLS) |
| Yahoo Mail | imap.mail.yahoo.com (993, SSL) | pop.mail.yahoo.com (995, SSL) | smtp.mail.yahoo.com (465 or 587, SSL) |
- Gmail: IMAP is always on for personal Gmail accounts. POP must be enabled in Gmail settings under Forwarding and POP/IMAP.
- Outlook.com: POP and IMAP access is off by default. Turn it on in Outlook.com settings, and use an app that supports Microsoft sign-in (OAuth), since basic password sign-in is no longer accepted.
- Yahoo Mail: Most third-party apps need an app password, which you generate in your Yahoo account security settings.
Connection failing? In most cases the port and encryption setting don’t match, for example port 993 with encryption set to “None”. Check that the pair matches the table above, and that a firewall or antivirus isn’t blocking the port. If you are setting up outgoing mail, our guide to SMTP explains how sending works.
When Should You Use POP3?
POP3 is great for users who prefer storing emails on a single device, like a desktop or laptop. It’s often used in environments with limited internet access because once the emails are downloaded, they can be accessed offline. POP3 downloads emails directly to your device, ensuring that once retrieved, they’re available for good. This protocol is also helpful for users who want to free up space on the mail server by keeping emails locally.
When Should You Use IMAP?
For those who frequently access their email from multiple devices—such as smartphones, tablets, and computers—IMAP is the better option. Unlike POP3, which downloads emails to the local device and removes them from the pop3 server, IMAP email accounts keep the emails on the email server, allowing you to view and manage email messages across platforms without fully downloading them to each device. This makes it an efficient choice for handling large inboxes and ensuring that your email provider retains copies of your emails for later use.
With IMAP, users can check your email from any device, and actions like reading, deleting, or moving emails are automatically synchronized across all devices. When you read an email on your smartphone, for instance, it will be marked as read on your tablet and computer as well. This is particularly advantageous for business users or those who travel frequently and need their email service to be available on the go. The protocol also allows you to store the email on the server, ensuring that you have copies of your email accessible at all times, even when using a new device.
Additionally, IMAP works seamlessly with email apps such as Outlook or Gmail, which are used by email clients to let people access email and manage their inboxes. IMAP’s ability to store emails on the email server is one of its biggest advantages, as it allows users to get an email or read your email on one device and continue working with it on another. This server-side synchronization ensures that all actions are mirrored across devices, giving you a seamless experience.
Moreover, both imap and pop3 are email protocols that email clients rely on to retrieve email from the server. The key difference between IMAP and POP3 lies in how they handle email storage. While pop3 downloads the email to a local device and often deletes it from the pop server, IMAP also keeps a copy of the email on the server, allowing continuous email access across platforms.
For users who need to send an email, your client uses a separate protocol, the Simple Mail Transfer Protocol (SMTP), whichever of IMAP or POP3 handles incoming mail. SMTP is used to send email from your client to the smtp server and on to the recipient. By choosing IMAP, you can not only access your emails from multiple devices but also ensure efficient email management, even when dealing with large email attachments or extensive inboxes. POP works well in specific scenarios, but for users who need multi-device functionality and fast syncing across devices, IMAP functions as the more flexible and versatile option.
IMAP vs. POP3: Which Is Better for Accessing Email on Multiple Devices?
When it comes to accessing email across multiple devices, IMAP is far superior to POP3. Since IMAP stores emails on a remote server, users can access the same messages from any device connected to the internet. This feature makes IMAP ideal for people who work in different locations or need to manage email on both personal and professional devices.
How Email Clients like Outlook or Apple Mail Handle POP3 and IMAP
Both Outlook and Apple Mail allow users to set up their email accounts using either POP3 or IMAP. If you set up your account with POP3, emails will be downloaded and stored locally on your device. On the other hand, with IMAP, your email client will sync emails from the remote server, making them accessible across devices. Email clients also offer the option to leave a copy on the server, which can help maintain flexibility with POP3 accounts or restore emails if mail doesn’t load or open.
Can You Switch Between POP3 and IMAP?
Yes, users can switch between POP3 and IMAP. However, it’s important to note that changing protocols can affect how your emails are stored. When moving from POP3 to IMAP, you’ll need to make sure that the emails stored on your local device are backed up, because POP3 usually deleted them from the server after download, so they won’t appear in your new IMAP folders. Most email clients let you move local folders back to the server once IMAP is set up. Similarly, when switching from IMAP to POP3, you’ll want to ensure that all necessary emails are downloaded from the email server.
Summary: Choosing the Right Protocol for Your Email Needs
Choosing between POP3 and IMAP depends largely on how you prefer to manage your emails. Here’s a quick summary of the key takeaways:
- POP3 is best for users who prefer to download and store their emails locally, offering full offline access but limiting usage across multiple devices.
- IMAP is the better choice for those who need to sync emails across multiple devices and prefer to keep emails stored on a remote server.
- Your choice will also depend on the email client you use and whether you prioritize storage on your device or the mail server.
POP3 and IMAP govern how you receive email. If you’re also sending campaigns to a list, that’s a different job entirely — and the platform you pick decides your deliverability and your bill.
Key Points to Remember:
- POP3 downloads and deletes emails from the server, making it suitable for single-device use.
- IMAP syncs emails across devices, keeping a copy of emails on the server for easy access from anywhere.
- Choose POP3 if you need offline access and don’t use multiple devices.
- Choose IMAP if you want your inbox kept in sync across multiple devices.
- Always ensure that emails are backed up before switching between the two protocols.
By understanding the key differences between POP3 and IMAP, you can make an informed decision about which protocol works best for your email habits, ensuring seamless communication in your professional or personal life.
Frequently Asked Questions
What is the main difference between POP3 and IMAP?
POP3 downloads email to one device and usually removes it from the server, while IMAP keeps email on the server and syncs it across every device, as Mailercloud’s guide explains. With IMAP, reading, moving or deleting a message on your phone shows up on your laptop too. With POP3, each device keeps its own separate copy.
Should I use POP3 or IMAP?
Mailercloud recommends IMAP for most people, because almost everyone now checks email on more than one device. Choose POP3 only if you read email on a single computer, want a full offline archive, or need to keep server storage low.
What ports do POP3 and IMAP use?
According to Mailercloud’s guide, IMAP uses port 993 with SSL/TLS or port 143 without it, and POP3 uses port 995 with SSL/TLS or port 110 without it. Outgoing mail goes through SMTP on port 465 or 587. Use the encrypted ports, 993 and 995, whenever your provider supports them.
Is IMAP more secure than POP3?
No. Mailercloud’s guide notes that both are equally secure when you connect over SSL/TLS on ports 993 (IMAP) or 995 (POP3). Security depends on the encryption setting, not the protocol. The real risk with POP3 is losing mail if your only device fails, since the server copy is usually gone.
Does POP3 delete emails from the server?
Usually, but not always. As Mailercloud’s guide explains, most email clients delete messages from the server after a POP3 download by default. Many, including Outlook and Apple Mail, have a “leave a copy of messages on the server” option you can turn on.
Can I use IMAP and POP3 at the same time?
Yes, with most providers, as long as each device uses one protocol. Mailercloud’s guide recommends checking your POP3 settings first: if POP3 deletes messages after downloading them, they will also disappear from every device that uses IMAP.
Does Gmail support POP3 and IMAP?
Yes. Mailercloud’s guide notes that IMAP is always on for personal Gmail accounts and uses imap.gmail.com on port 993. POP3 must be turned on in Gmail settings under Forwarding and POP/IMAP, and uses pop.gmail.com on port 995.
Do POP3 and IMAP send emails?
No. POP3 and IMAP only receive email. Sending uses a separate protocol, SMTP, as Mailercloud’s guide explains. Every email account setup has an incoming server (POP3 or IMAP) and an outgoing SMTP server, usually on port 465 or 587.
As a Marketing Director, I develop and implement marketing strategies, conduct market research, and manage a team of marketing professionals. With a successful track record of launching campaigns that drive revenue growth, I bring my marketing expertise to blog writing, creating engaging content that promotes the brand and its products/services.
