Why can I not send mail to an address which contains multiple sub domains, for example, machine.server.domain.dom?
The reason for this was that the administrator had put an entry of *.*.*.* in the list of aliases for his domain. It is surprising in fact that he was able to send mail anywhere as it should all have been treated as local.
Please ensure if adding an IP as an alias to a domain that only a full IP address is added. This could be necessary for instance if a machine has more than one NIC in it, do not use wildcards at all with IP addresses in this situation.
Keywords:sub domains, sending, unknown user