[ale] What's the mail port?

[Dylan Northrup]

This is one of my interview questions.  Port 25 is for mail.  If you forget,
you can check /etc/services for well known services.

A long time ago, (18.11.06), in a galaxy far, far away, Jim wrote:

:=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.
:=_______________________________________________
:=Ale mailing list
:=Ale at ale.org
:=http://www.ale.org/mailman/listinfo/ale
:=

-- 
Dylan Northrup - docx at io.com - http://www.io.com/~docx/
"Harder to work, harder to strive, hard to be glad to be alive, but it's 
 really worth it if you give it a try." -- Cowboy Mouth, 'Easy'