SMTP Protocol Returned a Permanent Error 550

[ecmjs]

We are running a Domino server with Notes 5 front end. I am unable to send email to one particular site. On each attempt I get the message:
SMTP Protocol Returned a Permanent Error 550 Access denied
I'm able to run nslookup from the mail machine. And send e-mail to the domain by hotmail. I can't find anything in the help or on the web about this? Does anybody know why this is happening?

 

[apinkerton]

It is pretty simple really, your error message says it all - "SMTP Protocol Returned a Permanent Error 550 Access Denied" literally means that you are not allowed to send mail to that domain. If it is an external domain to your own i.e. you are sending outside your company, then you may be on a "relay" blacklist. These are lists that have been compiled - usually automatically - that are know for relaying spam mail. There are a small number of these lists about, but I couldnt point you in the right direction, I only know of the existence of them. You will need to write to the list owner if you are on the list and have yourself removed. You can also subscribe your servers to these blacklists and stop spam entering your company that way as well - sometimes this can be done from the firewall. This may or may not fix your problem, but it is a place to start looking.