No, it isn't. /etc/hosts is not used by Courier. If your problem was related to IPv6, then you can't infer anything about DNS or the hosts file from that problem. They're unrelated.

Reindl Harald wrote:

Is localhost the only nameserver in /etc/resolv.conf?

What Sam was trying to tell you is that your name servers must be configured properly. Often when you see delays in TCP connections, that delay is caused by the server looking up the client's IP address in DNS and not getting a timely response. Courier also looks up the name of the user trying to connect using the "ident" protocol. That lookup can also cause delays if your firewall drops packets to that port (the connection has to time out rather than failing immediately).

In the future, when you're asking other people for their help, it pays to be patient and cooperate with their requests for information. In the case where language is an obvious barrier, you may have to be more patient, because you may misinterpret what you're being asked for (example: identd "authd" and courier's "authdaemond").

It isn't, though. Courier does lookups entirely through DNS. It doesn't use the C library's NSS routines, so the hosts file isn't used.

No, it isn't. /etc/hosts is not used by Courier. If your problem was related to IPv6, then you can't infer anything about DNS or the hosts file from that problem. They're unrelated.

That's mostly true. nslookup does get its results from DNS. However, being right is not an excuse to be rude. If I were you, I would consider an apology to the list. You may well need support in the future, and you're more likely to get that from a cooperative community if you maintain a good relationship.

Actually, your ISP's DNS *should* resolve localhost. RFC 1912 clarifies this name server requirement. The hosts file works for simple name lookups through the C library's NSS routines, but that's not what Courier uses.