Application Development Software

Hello,

Really i need help
can't send mail to some server like yahoo,hotmail ... , always get this error:

Your message cannot be delivered to the following recipients:

Recipient address: ***********@alcatel-lucent.fr
Reason: SMTP transmission failure has occurred
Diagnostic code: smtp;554 5.7.1 This message has been blocked because the HELO/EHLO domain is invalid.
Remote system: dns;mail.****.com (TCP|194.176.**.2|54121|212.59.**.188|25) (ice.****.lt ESMTP Sendmail 8.12.11/8.12.6; Mon, 23 Jan 2006 21:54:38 +0100 [CET])

Which fault is it: my webmail's server or receiver's mail server?

Pastel.