I still prefer POP3
But what about local spam detection?
As you prefer to use a POP account, if your online mail box doesn’t have very good mail filtering, then apart from the basic Spam filtering in eM Client in Rules and / or adding your own rules manually (where you can setup rules to block spam via header info, subject or body info), some eM Client users alternatively use eg: Mailwasher Pro which they say works very well for them with POP accounts.
See my post in the following thread for their information on that via their links.
Also see my screenshots “in that thread” for how to disable the POP account checking on startup to then allow Mail Washer or whatever other external Spam Filtering program to work prior to manually downloading POP mail into eM Client.