What is IMAP and POP3? Print

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POP3 and IMAP are two different protocols used to access e-mail. POP3 and IMAP function very differently from each other and each one has its own advantages. POP3 is useful for checking your e-mail from one computer at a single location. IMAP is the best option when you need to check your e-mail from multiple computers at different locations such as at work, home, or on the road.


POP3 works downloading your email messages from the server to the email client on your computer (such as Mozilla Thunderbird, Outlook, Mail, etc...) and removing them from the server (by default), so you can free up the space on your server each time you check your email. All your emails then are stored on your computer and they are not accessible from other locations. You can also configure your email client to leave the last emails on the server; for example you can tell it to leave the emails from the last 30 days, so you can still access them through IMAP with another computer or phone. With this last option, through IMAP you can only see the last incoming emails and not the ones that you sent from your main computer.

The POP3 option is good to access your received emails even without being connected to the Internet because you have all your emails locally on your computer and it's also good when you connect to the Internet through a dial up service or any other connection and you are charged for your connection time.


IMAP lets you view the headers of the new messages on the server and then retrieves the message you want to read when you click on it. When using IMAP, the mail is stored on the mail server and you're able to see your received and sent emails from different computers and from webmail.

Today email client software (again such as Mozilla Thunderbird) can still store your emails locally on your computer if you enable that option.

The main difference form POP is that the emails are not deleted from the server when you download new emails. With IMAP, you use the storage space on your server and you can free up space only by deleting emails manually or moving them to a local folder.

When should I use POP3?

  • When you only check e-mail from one computer at a single location.
  • You want to remove your e-mail from the mail server.
  • You connect to the internet through dial up and are charged for connection time.

When should I use IMAP?

  • When you need to check e-mail from multiple computers at multiple locations.
  • You use Web mail such as Gmail, Yahoo or Hotmail.
  • You need to preserve the different e-mail folders you have created.

Tips for better performance

Keep your Inbox small! This is especially true for POP3 and will speed up your e-mail retrieval. Checking the e-mail is directly dependent on how many e-mail messages are in your inbox on the mail server.


  • Try to reduce your inbox size. POP'ing large mail boxes consume excessive server resources.
  • Set to remove mail from server at the end of every month or even sooner.
  • Do not check your email more frequently than every 15 minutes.


  • Do NOT check all folders for new messages! This slows your e-mail substantially.
  • Organize your mail into folders, and archive your older messages. This speeds up e-mail retrieval by minimizing the number of messages in the inbox.

Questions and Answers

Q: Can I have an email account configured in both POP and IMAP?
A: Yes, you can. You could have set up your POP account to leave a copy of the emails of the last 30 days on the server and have both IMAP and POP configured in your main computer. Then you could set up the same email account by IMAP on your tablet, smartphone and another computer, so you can check your emails from anywhere and when you reply from those places, the message is stored on the server. Then you can retrieve the sent message from the IMAP account on the main computer and move it to a local folder, if you want.

Q: Can I change my actual configuration from POP to IMAP or from IMAP to POP?
A: No, you can't do that. If you are accessing, for example, your email with a POP account and you want to access your email by IMAP, you should configure a new email account on your email client, even if it's the same email account and you can have both POP and IMAP operating at the same time. Once you've set up the email on your preferred email client, you cannot change the protocol (POP or IMAP).

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