Should use use IMAP or POP for your email? Here are some details about both to help you choose:
IMAP email access coordinates between the server and your mail application. Messages that have been read/deleted/replied to will show up as such, both on the server and in the mail application. That means your email program, smartphone, and webmail will all be synched.
POP3 does not coordinate with the server. Messages marked as read/deleted/replied to in on your computer mail program will not show up as such on the server. This means that future mail downloads with POP3 will show all messages as unread. You should make sure to set your email program to delete mail from the server either immediately or after a certain number of days so it doesn't build up on the server and use up all your diskspace. You can see mail on the server using webmail.
With IMAP accounts you can access mail from multiple devices all at the same time.
The POP protocol is single access method. To close the connection on one device you may have to exit the email program or disable auto-email checking and only check it manually so you know when the connection is open and locking out other devices.
POP is not designed to retain mail on the server. IMAP allows multiple simultaneous access with server folder features built in.
POP - no folders
IMAP - folders
POP - single access
IMAP - multiple concurrent access
POP - "read" flag client-based
IMAP - "read" flag server based