My e-mail account, I get an error message. It says smtp server rejected the password for my yahoo address. I just changed the password for my yahoo address and for apple. Both are the same. I restart computer and still have same error message. WhatdoIdo?

Why do I get an error message on my Apple e-mail and ical. It pops up and says smtp server rejected my password for my yahoo account. I changed my password at yahoo and apple. Both passwords are the same. I did this 9 months ago and didn't do anything about it because I can see my e-mails at Yahoo. Then I changed the password today (Both Yahoo and Apple). I shut the computer down for 2 hours, and I still get the same error message. This is very annoying. What is with this thing.? Now my ical is also rejecting the password. But I know it works because it worked on icloud. Very annoying problem. Is there a solution?