Greg A. Woods: > There _should_ be one PTR for every _valid_ hostname using a given IP > address.
Statements such as above remind me of silly knights fighting windmills. There is a difference between "right" and "useful", and it even depends on where they are used - server or client side. Multiple server A records are useful. More in the case of HTTP, less in the case of SMTP which uses indirection via MX records. (For a discussion about domain-in-a-box applications, see some actual measurements that I did earlier this year). One PTR per A record is not useful. The server end will not know what client name to use. On the other hand, it is right when every PTR record has a matching A record that resolves to (among others) the PTR record's address. Wietse