imail moving messages constantly 1in 58

My imail on my macbook pro MAC OS high Sierra 10.13.3 has been moving messages 1 in 58 sometimes it shows 45 or 38 but never seems to complete the task. I read previous posting but I am not that savy on some of their suggestions. I do have my imail connected to At&T yahoo mail. I also noticed that my email account doesn't synchronize as it should. When I am on my mac in imail which is my yahoo email, shouldn't it be the same on my windows and my online att.net which is all the same emails? IDK anyone with a suggestion would be most helpful to me. Thanx.