What Does ' Illegal host/domain name 'mean?

[whatdidyousay!]

I am part of the group of people on an email list and I send out an email tonight and got a email saying one email could not be send because an "Illegal host/domain name was found", what does that mean? It for the landfill that smelling again.

 

[JMH]

Probably means the company has blocked this person's email address. I have seen that before.

 

[Calvin]

If you see error code "544" that means it's blacklisted or not allowed to send.

I am part of the group of people on an email list and I send out an email tonight and got a email saying one email could not be send because an "Illegal host/domain name was found", what does that mean? It for the landfill that smelling again.