Will IMAP allow me to read email on my device, but NEVER delete it from the server, and let me archive ALL email on my home PC?
Ummm...yes and no. The short, simple answer is "yes".
IMAP is different protocol. Most prefer it over POP, but there are advantages and disadvantages to both. On top of that different email clients handle the use of the protocols differently, and different email services can vary on the implementation of these protocols to some degree as well... so it can be hard to give a straight "yes" or "no" answer to your question.
With POP, messages are downloaded by the client as they arrive in your inbox. The full message is downloaded, and what you're pretty much left with a exact copy of your inbox that you can access via the mobile client. An advantage to this is that you could, potentially, view the entire contents of your inbox even if your POP client is offline (at least whatever content you've already downloaded). If you delete/move/etc an item from your POP client, a command has to sent back to the email service if that same action is to be replicated. One big disadvantage of this is that there is no way to sync offline activity, and if you want to access the account via multiple devices/clients, that can cause issues as well. Also, since the full message is downloaded, you may have to frequently delete old messages if you have limited storage for email on the client.
IMAP is more of synced copy of your online inbox. Whenever you open the IMAP client, you should be seeing the exact same data that is on the server. IMAP clients will generally NOT download all messages from the mail store. Rather, messages are downloaded on demand, usually to temporary cache. Some clients can be set up to download a set number of new messages (possibly with governors on size and/or attachments) to ensure availability if the client goes offline, but again, these messages are generally saved to a temporary cache that just refreshed as new messages arrive. When you click on a message, the server is contacted, the contents are downloaded, the message is read. With most IMAP clients, if you delete a message from the device, you will also delete it from the server -- some clients have options to change this behavior, but I guess the real point is that if IMAP is set up correctly,
you shouldn't have to worry about deleting messages via the client, because they're not being permanently saved to the client in the first place. It operates much more closely to how the web client would work. What you see is what you get...If you're online, you can view and search the entire mail store, but if you're not, you can't access much of anything.
For example, I have a work email account set up using IMAP via the K9 email app. It's set up to fetch the first 25 messages in my inbox, and to download full messages automatically up to 1MB (manual download of attachments and larger messages). I can easily tell the client to fetch more messages if I'm looking for something older, as well as search my entire mail store (inbox, outbox, trash, etc). I never really have to worry about deleting anything, because it's not really saving that much data to the device itself...as new messages arrive, the older ones are removed from the primary view of the K9 client.
I'm not sure if this makes as much sense as I would like, but again, the long story short is that with a true IMAP setup, you shouldn't
have to delete messages from the device UNLESS you want them deleted from your actual mailbox on the server.
You can probably get a more exact answer if you specify what email client you're using and possibly what ISP mail service you're connecting to.
Facebook
Twitter
Instagram