IMAP vs. POP
With IMAP your e-mail is stored on your host’s server while with POP you download your e-mail to your own computer, which is then deleted from the main server (unless you tell it not to). Therefore IMAP is better if you are getting your e-mail from several computers or devices like an iPhone or iPad.
With IMAP your e-mail is in the same condition from wherever you get it. For instance, if you read your e-mail but didn’t delete it, it will still be on the server as already read, no matter where you are viewing it. But if you are using POP and you read your e-mail on your iPhone and then later checked your mail on your iMac, it will show up again as unread. How very annoying. UpperHost has a simple explanation of IMAP vs. POP.
It is best to start out with IMAP.
Switching from POP to IMAP can be quite a challenge. Here’s my tale.
I was using a local hosting company, then switched to GoDaddy. I always used POP because the local company didn’t want me storing e-mails on their server. One of the reasons I switched.
I read an article in MacWorld Magazine on The IMAP Advantage and decided to make the switch. At the time I had over 13,000 e-mails in my main e-mail account. It was suggested I save these in a folder on my computer. Sorting out 13,000 e-mails would take too much time so I tried dragging them to a generic folder and received an error message.
GoDaddy said they it would be okay to make the POP account inactive while activating the IMAP account. And this worked fine. But then something happened and a few days later all 13,000 plus e-mails became blank. They were missing. Yikes, I said to myself.
With frantic calls to Apple Support I managed to restore most of my old e-mail to my computer from my Time Machine backup. How ironic that the main reason I switched from POP to IMAP was to have a safe back up for my e-mails and in the process I lost (temporarily) all my old e-mail.
So always be sure to save your e-mail to your computer if you are switching from POP to IMAP. And have a backup plan. Hard drives do fail and e-mails do disappear.