How does one deal with a discrepancy in email account types (IMAP vs. POP) between multiple Apple devices?

I am using Mail on three Apple devices (Mac Mini, iPhone and iPad, all three with the latest OS). My mail service is through my local ISP and my primary email address and account is through that provider. I also have an iCloud account, but have avoided using it for correspondence. Problem: I can send mail from all three devices, using my local email account. I can receive mail for that account on all three devices. The account on the Mac Mini does not receive mail. I have checked the server settings on all three devices. The one significant difference between the Mac Mini settings and the other is: The MacMini local email account is designated as a POP type. It is an IMAP account on the iPhone and iPad. The iCloud account is classed as IMAP on the Mac Mini and shows no designation on the iPhone and iPad. The ISP says the primary account should be an IMAP ope. I find no information how to make the change on the Mac.

Advice?