I use usually the Outlook Express for mailing.
Lately I tried to send a message to a certain address, but it returned to me saying :
<The message could not be sent because one of the recipients was rejected by the server. The rejected e-mail address was 'editor@tipa.co.il'. Subject 'sefer-li', Account: 'pop.012.net.il', Server: 'smtp.012.net.il', Protocol: SMTP, Server Response: '550 5.1.1 unknown or illegal alias: editor@tipa.co.il', Port: 25, Secure(SSL): No, Server Error: 550, Error Number: 0x800CCC79>
this happened several times. I tried to send messages from the same OE program to other addresses and they went OK. The OE worked properly with them. I suspected that the bug is at the recipient, but then I sent the same message to the "editor@tipa.co.il" from my gmail, and it went OK, and I received an immediate answer.
What can be the problem? Why was the address not recognized by OE?
Please advise
Thanks

Maybe ".co.il" isent recognised as a "legal" adress?

I found this which might help: Outlook Express Error 0x800CCC79: Not Able to Send Mail? Then Turn on SMTP Authentication

Good luck!