I’ve been using Mac Mail since getting a Yahoo Mail Plus account. I had no prior problems writing, sending and receiving emails since setting the account in Mail. However, for two days now I started having problems sending and receiving my Yahoo mail in Mac Mail. When I write a test email in Mac Mail and send it, it takes an hour and half for it to get back. When I use webmail to do the same, the test message is received instantaneously.
I have other POP accounts in Mac Mail (such as gmail and telus) and I have no problems sending and receiving a test email.
I have not modified any settings since setting this account months ago. I’ve tested my internet connection using the Connection Doctor in Mac Mail and everything works.

this isnt a problem on your computer, it is a problem on the server you are landing on as it is over busy or being worked on due to failure
The time lags you are having should clear up soon