Dave Warren skrev den 2013-10-30 22:08:
192.2.0.55 has a TLD... 55.
dig 192.2.0.55 what name have the nic ns then ?
My interpretation is that when you have an IP specified properly [192.2.0.55], it's treated as a IPv4 address literal and is deliverable. When you have a bare IP, 192.2.0.55, you follow normal DNS lookups.
[192.2.0.55] is treated as a valid domain, but dont dig it :)
Since the 55 TLD doesn't exist, you get a NXDOMAIN from the root-servers and reject the mail.
you could say it that way yes, but its still incorrect
