Undeliverable Mail

[123gad]

I have one user who is e-mailing to the same person back and force for 2 days, today she received the following error message:

Unable to send to recipient@...org. The remote server reported the following error: 553 sorry, that domain isn't in my list of allowed rcpthosts

What exactly does it mean, is there a problem on our end,our e-mail is hosted off site or is it on the recipients end. we are using Outlook 2003, why would it work to sent 4 or 5 messages and out of the blue it is undeliverable. My CEO is not very happy about it and want to have some answers I don't have, but I hope there is someone to help me.

Thanks again for all your help.

 

[franklin97355]

553 sorry, that domain isn't in my list of allowed rcpthosts could mean the address was spelled incorrectly or the receiving mail server has been changed. Did you try sending this from another computer? That would be my first step.

 

[123gad]

Thanks for your response, yes I tried from a different machine, and it worked, same address I copied and pasted it from the undeliverable.
Any ideas why it wouldn't sent from the other machine?