[ale] What's the mail port?

[Jim]

I know, dumb question.  Here's the problem.  I've been doing 
Unix/Linux/Solaris/Sunos/Irix/UnicosXenix sys admin tasks for better 
than 20 years but always someone else has taken care of mail so other 
than some simple stuff like configuring a pop client, I've not messed 
with mail.
  So I decided I needed more control over my life or at least my 
computers and I've subscribed to a VPS to get my feet wet.   I've locked 
it down very tight.  So tight that mail isn't getting into the system 
because the port isn't open.  I don't understand the log well enough to 
know what port it is preventing access to.  Here's a line:

Nov 18 12:41:04 fdcga kernel: RULE 8 -- DENY IN=eth0 OUT= 
MAC=fe:fd:45:5d:7f:cd:00:02:fc:64:d8:af:08:00 SRC=205.152.59.68 
DST=69.93.127.205 LEN=40 TOS=0x00 PREC=0x00 TTL=49 ID=20197 DF PROTO=TCP 
SPT=16109 DPT=25 WINDOW=25416 RES=0x00 RST URGP=0

And another one.

Nov 18 12:45:06 fdcga kernel: RULE 8 -- DENY IN=eth0 OUT= 
MAC=ee:fd:45:5d:7f:cd:00:d0:ba:1f:b5:cf:08:00 SRC=xx.xx.xx.xx 
DST=xx.xx.1xx.xx LEN=48 TOS=0x00 PREC=0x00 TTL=117 ID=28102 DF PROTO=TCP 
SPT=3221 DPT=135 WINDOW=64240 RES=0x00 SYN URGP=0

  If DPT is the port, then 25 is logical, but I don't want to open 25 up 
without first knowing I'm not going to be running a open relay.  So I 
guess my questions are, what ports to I need to open to make incoming 
mail work and how do I configure postfix so I'm not running an open relay? 

This is a ubuntu 6 install I think.

Thanks,
Jim.