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POP3/IMAP Comparison

Both POP3 and IMAP are protocols for accessing your mail. They connect to the same place, and read the same messages—but one of them is speaking French (POP3) and the other Klingon (IMAP).

There are pros and cons to both.



  • It works well in Microsoft Outlook.
  • You save a copy of your messages locally by default.
  • You never run out of space on the server because messages are removed from the server when you read them.


  • You cannot share folders between mail clients and/or the webmail.
  • Backups are your own responsibility.
  • If you want to retrieve the same messages from more than one location, you need to leave your messages on the server (in the Inbox) for some specified amount of time. This results in the Inbox becoming clogged and slow.
  • Poorly-written mail software (e.g. MailMax) can get confused when two or more devices access the same mailbox at once. This can result in a permanently-locked mailbox.
  • It's an old protocol, superseded in all ways by IMAP. Nobody is making POP3 improvements any more.



  • We back up your messages.
  • You see the same folders everywhere, even in the webmail.
  • Using sieve, you only have to create your filters once and they will work everywhere.
  • New features are still being developed for IMAP.
  • IMAP was designed to be access concurrently.
  • You can still save a copy of your messages locally, although this usually has to be configured.


  • Outlook is a bad IMAP client.
  • You must keep your inbox clean by organizing your messages into folders. If you don't do this, access to your inbox will get slower and slower over time.

Switching from POP3 to IMAP

There are some concerns that only apply when switching:

  • Your old mail is stored on your machine. There are two ways to handle this.

    1. Copy all of your old mail up to the server. This will take a long time.
    2. Keep your local mail archived under a separate account in your mail client. You'll have to remember to look in the other account for your old mail.
  • You should switch all of your devices at once, so that none of them continue to delete your messages from the server.