My Windows Live Mail will receive emails but has stopped sending emails as of April 18/18.  What could be wrong?  I am running Windows 10.  The following is the error message I receive.

An unknown error has occurred.

Server: 'smtphm.sympatico.ca'
Windows Live Mail Error ID: 0x80070057
Protocol: SMTP
Port: 25
Secure(SSL): Yes

[Original subject: Windows Live Mail problems]