"If you'd like to understand better what the email protocol 'IMAP' is all about, here is an article that gives a good description of it," begins Jim Hamm with his trademark grin. He acknowledges, "Understandably, you may not care. If the client you use for email works for you, and you're not inclined to change, then just bypass this article.
"As an ancillary note, I use IMAP— and like it — but no longer use an email client, like Apple's Mail, on any of my computers or iOS devices. I use the web-based Gmail as my email client. That is, I log into Gmail on their server and do all my email reading, etc., there — not on my computer. I find this to be much simpler: all my emails are always coordinated and in-sync between all my devices, all of the emails I've ever received are permanently stored there (mighty handy to look up an old email from a long time ago), and I never have to worry or fuss with doing an update to my email program -- Google takes care of that for me — and I never have to tell anyone to 'hold sending any email to me while I travel' — I've got plenty of storage space in Gmail."