On Mon, Jul 26, 2004 at 02:04:55PM +0200, Marco d'Itri wrote: > On Jul 26, Anthony DeRobertis <anthony@derobert.net> wrote: > > > No, it's not. RFC 2821 Section 4.1.1.1 clearly says an IP address is > > allowed: > This does not mean it's a good idea for server-server SMTP connections No, but the OP was about Thunderbird, which is certainly not a server-server SMTP connection.