Comment 4 for bug 144431

This bug report is valid. The RFC does not prohibit labels that don't start with a letter; it merely recommends against them. The definition of "label" mentioned above is part of a guideline introduced with this text:

"The following syntax will result in fewer problems with many
applications that use domain names (e.g., mail, TELNET)."

Points in favor of supporting domain names that don't necessarily follow those guidelines:

1. There are actual domains out on the Internet running web sites with such domain names (several blogs at blogspot.com spring to mind)
2. Such domains resolve on other OSes (not just Windows, but also OS X).
3. Direct DNS queries (dig, host, nslookup) on Linux work fine with such names.
4. Even gethostbyname() on Linux works for such names when they're in the local /etc/hosts file. Possibly in NIS maps as well.

Point 4 is especially telling; I don't see any reason for gethostbyname() to introduce a restriction between two interfaces when that both operate correctly without the restriction. Especially not a restriction that prevents access to actual web sites. Telling users that "The owner of that site shouldn't have named it that" is not helpful.