The Joy and Sorrow of IMAP - Emailers Anonymous
First, the definitions:
POP, or POP3: Post Office Protocol 3, the most commonly used email protocol for retrieving remote email to a local client over a TCP/IP connection.
IMAP, or IMAP4: Internet Message Access Protocol, an email protocol for accessing email on a remote server using a local client over a TCP/IP connection.
While the two definitions seem very similar, take note of the difference. POP is used for retrieving email to the local client, whereas IMAP is used to access email located on a remote server.
When you use POP, your email comes in to you local client, and typically the remote version is purged. There is no concept of multiple clients having identical synchronized versions of your inbox and email folders.
When you use IMAP, your email actually lives on a remote server, and is not purged. You can access it with a local client, which downloads a copy of your messages, and synchronizes the contents of your local mail store to that of the server's. Changes that you make locally are reflected on the server, and if you wanted to you could connect with another device or email client that is capable of IMAP, and you will see exactly the same thing - all of your messages in your inbox and other folders will reflect exactly what is on the server.
Sounds pretty great, right? Well, yes. Most of us probably have some hardcore geek friend that has been extolling the virtues of IMAP for years, only to have it fall on deaf ears. Most of us have either never had the need for such synchronization, or have not had an IMAP capable mail provider.
For many people, however, having an iPhone in their life made it abundantly clear that having the ability to look at the same inbox on their computer and their mobile device would be extremely valuable.
Gmail's engineers must have thought so too, since it seems like not long after the iPhone was released, Gmail released IMAP access to the masses.
So, with all of the wonderful time saving aspects of IMAP, what reason could you give for not using it? For many, the answer is simple: there isn't one - using IMAP is the only way to go. But the problem of data synchronization that is tackled by IMAP is a sticky one, and one that can sometimes turn ugly.
There is certainly a sense of safety using a solution like IMAP that creates what amounts to multiple synchronized copies of your data. Think of it; if you have a problem on your local email client, simply purge it and start over, and IMAP will happily resynchronize all of your messages from the server. But that synchronization is a double-edged sword. If your local mail client goes haywire and starts doing strange things to your messages, those strange things get synchronized back to the server.
Yes, but does this ever happen? Unfortunately, yes. It's fairly rare, but certainly something to be aware of, and careful about.
For most active IMAP users, the sheer convenience more than outweighs the potential risk, and realistically there is no more danger when using IMAP compared with using POP and only having one copy (your local mail store) of your messages. In both cases, the smart thing to do is ensure you are keeping backups.
Many web hosts and ISPs now offer IMAP as an option, and reasonably large email folder limits. Some even offer unlimited email storage. If you're already using webmail and have flirted with using a desktop client like Outlook or Apple Mail, but didn't want to deal with having to make the switch, give IMAP a try. It can be really nice to work on a desktop application when you're at your computer, but also be able to log into a webmail interface and be dealing with the exact same email environment.