[IMail Forum] Advise required

[Ganesh]

I  tried to send  a mail and got the following error message:   "The message could not be sent because the server rejected the sender's e-mail address. The sender's e-mail address was '[EMAIL PROTECTED]'. Subject 'Re:  Application from Bilal Tabassum ', Account: 'mail.renoirgroup.com', Server: 'mail.renoirgroup.com', Protocol: SMTP, Server Response: '451 4.7.1 Please try again later', Port: 25, Secure(SSL): No, Server Error: 451, Error Number: 0x800CCC78"   Can any one suggest why this happened? I use Outlook Express and  Imail5.   Also advise where I can find the explanation for the "error number".   Thanks Ganesh