An unknown error has occurred.

Subject 'Re: Reply to your " any email I try and send
Server Error: 550
Server Response: 550 5.7.1 s26Eqsd3003777 This message does not comply with required standards.
Server: 'smtp.sasktel.net'
Windows Live Mail Error ID: 0x800CCC69
Protocol: SMTP
Port: 25
Secure(SSL): Yes

This has been happening for a month without me knowing - not good seeing as I am at work trying to email clients