For your desktop, if you have a large mailbox, OVER 5,000 messages or 5GB of space used, IMAP is the protocol you should use for your email. For your calendars or contacts you can use any other of the sync protocols (such as CalDAV and CardDAV) but for your email, you should use IMAP. IMAP has push-like support with the IMAP IDLE process, which pushes new messages to your desktop client at a set interval.
Trouble logging in? Simply enter your email address OR username in order to reset your password.
For faster and more reliable delivery, add email@example.com to your trusted senders list in your email software.