What is POP3 server?

A POP3 (Post Office Protocol version 3) server is a type of email server that is commonly used to receive and store email messages for end users. The main purpose of a POP3 server is to enable users to access their email inbox from any computer or device, even when they are offline or not connected to the email server.

What is POP3 server?

How POP3 Server Works

Here is an overview of how POP3 servers work:

Email Retrieval

  • Emails are received and stored on the POP3 server until the user is ready to download them.
  • When the user connects to the POP3 server via a POP3 email client (e.g. Microsoft Outlook, Apple Mail), they can retrieve and download messages to their local computer or device.
  • Once the user downloads the messages, they are usually deleted from the POP3 server to free up storage space. Some POP3 servers have an option to keep a copy of retrieved messages on the server.

User Authentication

  • To connect to a POP3 server, the user needs to authenticate themselves by providing their username and password. This allows the POP3 server to verify the user’s identity.
  • POP3 uses a TCP/IP network connection on port 110. Connections are usually encrypted using SSL (Secure Sockets Layer) on port 995 to protect user credentials.

Message States

  • POP3 servers keep messages in two states – “new” for messages not yet retrieved, and “old” for already retrieved messages.
  • Users can selectively download only new messages, keeping old messages stored on the server. This allows accessing messages from multiple devices.
  • Once a message is marked as “old”, the POP3 server keeps it in the user’s inbox until deleted either automatically or by the user.

Advantages of POP3

Some key advantages of using POP3 for email include:

  • Offline access – POP3 allows users to retrieve emails even when disconnected from the server. Emails are saved locally for offline access.
  • Portability – POP3 makes emails portable as users can access their inbox from any device or location after downloading messages from the POP3 server.
  • Storage efficiency – Deletion of messages from the server frees up storage space on the POP3 server once users have downloaded emails.
  • Backwards compatibility – POP3 is an older standard that is supported by almost all modern email clients and servers for backwards compatibility.
  • Simple to implement – POP3 is relatively simple to set up and use as a standalone protocol compared to more complex alternatives like IMAP.

Disadvantages of POP3

Some potential downsides to using POP3 include:

  • Single point of access – Users can only access their inbox from one device/location at a time. POP3 does not synchronize messages across multiple devices simultaneously.
  • Message management – Since downloaded messages are usually deleted from the server, users may lose messages if they are deleted accidentally from their local devices.
  • Security vulnerabilities – POP3 has some security weaknesses making emails potentially vulnerable to snooping unless using POP3S with SSL.
  • Storage constraints – POP3 accounts usually have storage limits on the server, restricting the number of messages that can be stored.
  • No remote access – Unlike IMAP, POP3 does not allow users to remotely access and manage their emails online when away from their main device.


POP3 and IMAP are the two most common protocols used for retrieving emails. Here is how POP3 and IMAP compare:

Parameter POP3 IMAP
Full form Post Office Protocol version 3 Internet Message Access Protocol
Message storage Messages are downloaded and deleted from server Messages remain on the server
Access Can only access inbox from one device at a time Multiple simultaneous device access
Synchronization No automatic sync across devices Changes sync across connected devices
Bandwidth usage Downloads complete messages Only headers are downloaded by default
Webmail access No webmail access Full webmail access supported
Advanced features Basic download and delete More advanced features like flagging, folders, searching etc.

How to Access POP3 Email

Here are the typical steps to access your email via POP3:

  1. Get POP3 credentials – Your email service provider or IT admin will provide the POP3 server address, port, and your login details.
  2. Configure email client – Input the POP3 settings into your desktop, web or mobile email app e.g. Outlook, Thunderbird, Apple Mail etc.
  3. Connect to POP3 server – Your email client will connect to the POP3 server on the specified port using SSL encryption.
  4. Log in – Authenticate using your username and password credentials.
  5. Download messages – Email headers will be listed. Select messages and download to your local device.
  6. Disconnect – Log out and disconnect from the POP3 server once you are done. Downloaded messages will now be available offline.
  7. Repeat – Follow the same steps to retrieve new email messages periodically.

POP3 Server Configuration

POP3 is usually implemented as software like Microsoft Exchange, Sendmail, Qpopper etc on the email server. Here are some key POP3 server settings:

  • Incoming port – Port 110 for unencrypted POP3. Port 995 for POP3S with SSL.
  • Outbound port – Port 25 for SMTP to send outgoing mails.
  • Authentication – Support for APOP, SASL Plain etc to authenticate and encrypt passwords.
  • TLS/SSL – TLS or SSL implementation for encrypted connections.
  • Storage limits – Mailbox size limits per user. Additional storage may be limited.
  • Message expiration – Automatic deletion of older messages based on elapsed time to manage storage.
  • Message download – Deleting messages from server after user download options.
  • Antispam and antivirus – Integration with spam filters and antivirus software.
  • Access controls – Allow/deny lists, restricted login hours etc to control access.
  • Logging – Activity logging for security and auditing.
  • Backups – Automated server backups to preserve messages and continuity.

Migrating from POP3 to IMAP

For users looking to move from POP3 to IMAP for greater functionality, here are some tips:

  • First set up an IMAP account with your email provider and configure IMAP access in your email client before disabling POP3. This allows a parallel transition.
  • Leave POP3 enabled temporarily during the transition to avoid any disruption and messages getting lost.
  • Once IMAP setup is complete, change all your email client devices and apps to use IMAP instead of POP3.
  • Backup your previously downloaded POP3 messages from all devices before finally disabling POP3 access.
  • Ensure any messages left on the POP3 server also gets moved to the IMAP server storage.
  • Confirm that IMAP access is fully functional from all your devices before finally disabling POP3 and migrating completely.
  • Update email client settings on all devices to remove the old POP3 account configurations. All email access is now via IMAP only.

With these steps, you can transition from POP3 to IMAP in a phased manner for a smooth migration.


In summary, POP3 is a simple and portable email protocol that allows downloading messages from a central server for offline access. However, its limitations around storage and single device access have led to IMAP becoming more popular. For advanced email access across devices, IMAP is generally recommended over POP3 now. Many email providers also support both protocols to give users a choice between convenience and more features.

Frequently Asked Questions

Q1: What port does POP3 use?
A1: POP3 uses port 110 for unencrypted connections. Port 995 is used for POP3 with SSL encryption.

Q2: Is POP3 secure?
A2: Unencrypted POP3 has some security vulnerabilities. Using POP3S with SSL/TLS encryption provides secure access and protects login credentials.

Q3: Can I access email from multiple devices using POP3?
A3: No, POP3 does not allow simultaneous access from multiple devices. Only one client can connect at a time.

Q4: Does POP3 allow accessing emails online?
A4: Unlike IMAP, POP3 does not allow accessing your inbox from a web browser online. A POP3 client is required.

Q5. Will my emails be deleted from the server with POP3?
A5: By default, most POP3 servers will delete messages once you download them locally. But this can be disabled to keep server copies too.

Q6: Is POP3 still used today?
A6: Yes, While IMAP has gained popularity, POP3 is still supported by email providers and clients for backwards compatibility.

Q7: Can I migrate from POP3 to IMAP?
A7: Yes, you can transition from POP3 to IMAP while keeping both enabled temporarily. This allows a smooth migration to IMAP’s more advanced features.

Q8: What is a POP3 email client?
A8: A POP3 client is an email app like Microsoft Outlook, Apple Mail, Mozilla Thunderbird etc that supports connecting to a POP3 server to retrieve emails.

Q9: Does Gmail support POP3?
A9: Yes, Gmail allows enabling POP3 access to download Gmail emails to a POP3 client like Outlook.

Q10: What is the difference between POP and SMTP?
A10: SMTP is used for sending outgoing emails while POP3 is used for retrieving incoming emails from a server.

Q11: Can I use webmail with POP3?
A11: Unlike IMAP, POP3 does not support accessing your email inbox directly through a web browser. A POP3 client is required.

Q12: How do I choose between POP3 and IMAP?
A12: If you need to access your email from multiple devices and locations, IMAP is better. For just downloading emails to a single computer, POP3 may suffice.

Q13: Is POP3 slower than IMAP?
A13: No, both protocols are fast enough for most use. The speed depends more on your network connection.

Q14: What are some good POP3 servers?
A14: Some commonly used POP3 server software are Microsoft Exchange, Qpopper, Eudora Internet Mail Server, Sendmail, qmail etc.

Q15: Can I keep emails on the server with POP3?
A15: Yes, POP3 can be configured to keep copies of retrieved messages on the server instead of deleting them.

Q16: Does POP3 support email folders?
A16: Basic POP3 has limited support for folders. But some POP3 servers allow folder management through proprietary extensions.

Q17: Is POP3 encryption secure?
A17: POP3S with SSL/TLS encryption provides good security and keeps your emails & passwords safe from interception.

Q18: Can I use POP3 on my phone?
A18: Yes, most mobile phones can be configured as POP3 email clients to download emails from your POP3 server account.

Q19: How do I set up POP3?
A19: Get your POP3 server details from your email admin or provider. Then configure your email app with the POP3 address, login credentials, and security settings.

Q20: Does POP3 download attachments?
A20: Yes, POP3 will download the full email including any text, attachments, images etc. But size limits may apply

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