An unknown error has occurred.

Subject 'Facade Renovation'
Server Error: 421
Server Response: 421 Unexpected failure, please try later
Server: 'smtp.earthlink.net'
Windows Live Mail Error ID: 0x800CCC67
Protocol: SMTP
Port: 25
Secure(SSL): No

I keep receiving this error message when I try to send email.  I receive just fine.  I am running Windows 7.   I am pretty computer illiterate and would appreciate a little help.