There is a lag on my emails

As of last night (January 8th, 2020) none of my emails came in after 5:30pm. Then they all came in at about 2:30am. Now, some seem to be coming through and others aren’t. Is there a way to tell where the issue is?? 

Go to Menu > Tools > Operations, and look in the Log tab for any errors. But is seems that if it was working, then for a few hours it wasn’t, then it was gain, the problem is most likely with the email server.