Emails deleted on iPhone still show on iMac mail

Just wanted to give an update on this. I decided to delete the email account on my iPhone and then re-add it back in, to see if that made a difference. It seems to have help a lot, but not perfectly. For the most part, most of the emails I get while on my iPhone and then delete, are no longer showing up on my iMac when I get home. There have been a few here and there that will still show up even though I deleted them while on my iPhone. I don't seem to have any issues at all when I view email on my iPhone when I'm at home, and then check email on my iMac later. The issues seem to be mostly when I'm checking email on my iPhone when I'm not at home, and then come home and check email on the iMac. Then I seem to have some email that was deleted on the phone showing up on the iMac. But deleting my email account on the phone and then re-adding it back in has helped quite a bit. Still a bit frustrating that it's not syncing like it should and don't know why it's not.

I went into my iMac mail and did a sync. That hasn't resolved anything. I also went on my iPhone and went into my email account, advanced and for "Deleted Mailbox", I changed it from the "on the server" trash, to the "On my iPhone" trash, thinking that would help resolve it. It hasn't. I just got home a short while ago, and all the emails I looked at while at work and deleted and then emptied the trash are there now on my iMac when I just launched email!!! **** It!!!! I'm wondering if on my iPhone, email account, advanced, where it says "Deleted Messages", I have selected "After one Day", if that's why they aren't completely gone and appear on my iMac? On my iMac, in Mail, Preferences, under my email account, it gives the option to "Erase deleted messages" "When Quitting Mail" which is what I have it set to. If I had that option on the iPhone, which I'm not sure why it's not an option (It has Never, After one day, one week, and one month), maybe that would resolve it??

I went into system preferences, Internet accounts, iCloud, and it asked me to enter my apple ID info and then said I was already logged in. The email I'm having issues with is an @att.net email account, which is set up as an IMAP email account, so it's not an iCloud email account.

One weird thing I've noticed is that if I'm at home checking email on my iPhone, any email I delete while on my iPhone seems to be deleted when I then check email on the iMac. The issue seems to be just when I'm at work or elsewhere checking email on my iPhone. Not sure why it would make a difference if I'm home or at work checking email on my iPhone. I would think it would all be the same and the iMac and iPhone should be synced no matter where I'm checking email. That is the whole purpose of an IMAP email account, correct?