This is a great question! Are you using the default email application on the phone or are you using a 3rd party email application that you downloaded from the Google Play store?
I am using the default EMail app, the one that comes stock with S8.
Well, I figured both questions out:
* To sync "immediately", you diagonally swipe the screen and it will cause a new sync
* I have my PC's Office Outlook using POP3 and it takes off the server whatever is there. When my Samsung S4 was alive, I also had it set up for POP 3 with delete from server when deleted from in box setting; it worked super. I tried that on my S8 and no joy -- hence my question. To get the same effect as my old S4, I finally figured it out that I had to use IMAP on my S8 -- so if I read something on my phone it stays on server and if I delete something on my phone, it comes off of server -- that way when I fire up my PC, all is well.
Kind of strange that to get the same effect I had to change to IMAP -- oh, well so it goes!
Nice find! I am glad to hear that you were able to figure this out. No one like to have to read/delete emails 2x!