I am trying to set up Gmail (web application) to work as the client for a Microsoft365 account. (Note: no I don't think this is a particularly good idea, but I am receiving a demand for this function, and if I'm unable to talk people out of their demands then I'd like to have a working solution in hand...)
I know that Gmail should work as a client if the Office365 account has POP3 enabled. (Also this.) I have confirmed that the MS Exchange account does in fact have POP3 enabled. So I was walking through the setup process, but I am stuck at the step where we see the checkbox labeled "Leave a copy of retrieved messages on the server". (Picture credit doteasy.com)
What would be the most correct way to set this checkbox? If "leave messages on server" is checked, I am worried that I will get duplicates of all received messages. If I do not click this box, then I am worried that the emails will no longer show up on any other clients besides Gmail. At present I can only try this out on a live account where I actually care about the emails on my email server and do not want to corrupt the mailbox.
What is the best way for me to proceed?