What's closing off port 25?

[Jonathan Q <jq@example.com>]

Inching toward running a local MX, I was taking
Sendmail out for a testrun today (standard RH 7.1 package 
8.11.2-14), and always get connection refused if
I telnet to port 25, unless it's from localhost.

/etc/hosts.deny and /etc/hosts.allow are empty.

The ipchains rules should be letting it in (also,
both shutting down ipchains and removing all rules
have no effect at all):

:input ACCEPT
:forward ACCEPT
:output ACCEPT
-A input -s 0/0 -d 0/0 22 -p tcp -y -j ACCEPT
-A input -s 0/0 -d 0/0 25 -p tcp -y -j ACCEPT
-A input -s 0/0 -d 0/0 -i lo -j ACCEPT
-A input -p tcp -s 0/0 -d 0/0 0:1023 -y -j REJECT
-A input -p tcp -s 0/0 -d 0/0 2049 -y -j REJECT
-A input -p udp -s 0/0 -d 0/0 0:1023 -j REJECT
-A input -p udp -s 0/0 -d 0/0 2049 -j REJECT
-A input -p tcp -s 0/0 -d 0/0 6000:6009 -y -j REJECT
-A input -p tcp -s 0/0 -d 0/0 7100 -y -j REJECT


The SMTP connection is getting to the machine,
so no access lists are in the way:

19:34:04.467447 eth0 < yamame.gol.ad.jp.46781 > uucp.yamame.org.smtp: S 4196896334:4196896334(0) win 5840 <mss 1460,sackOK,timestamp 53599200 0,nop,wscale 0> (DF) [tos 0x10]

Yeah, sendmail is running :-) -bd -q1h

It's probably something frightfully obvious that will make me
look stupid when discovered :-)  But between here and there,
I'm open to suggestions.

TIA,

Jonathan