Gene,

You've nailed your problem right there. Gmail handles POP3 and IMAP, even
for the same account, pretty much as though they're entirely different
servers. I've never understood what the actual mechanics of this are in
practice, but Gmail allows you to turn on options for both POP and IMAP
access for a single account, and when they are both on, each access method
works in "it's own little world." In practice it is never expected that a
single account will be accessed with both protocols. If Google had been
smart that radio button would allow only one of those two options to be
active. And as you've now learned from direct experience, when one is,
there's always a level of madness that ensues if mixed access via different
clients is used.

With any given account, if you're using IMAP, use it in each and every
client that accesses the account if you want things kept in sync.

--

Brian - Windows 10 Pro, 64-Bit, Version 2004, Build 19041

*Always remember that computers are just glorified light bulbs - they rarely
fail in continuous use and usually go pop when turned off and on.*

~ Technician with the username Computer Bloke, on Technibble.com