Logon Failure: unknown user name or bad password

Logon Failure: unknown user name or bad password

I'm having a problem regarding the email search it's saying that the username or password is incorrect but I already checked, and even then I'm still having problems I've already checked if the connection to the email server is blocked using: telnet mailservername:port(995) and I tried using kb: https://pitstop.manageengine.com/portal/en/community/topic/mail-fetching-and-mail-sending-issues-faced-by-office-365-users.
and I was not successful.