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i need senmail to listen on port 25 locally, but it shouldn't receive mail from outside. normally i install qmail, but this is my friend's box and he doesn't want it.
i have never understood sendmail. i've managed mail servers for 6 years, but have never used it. sendmail just makes no sense... i've done some searching on the web, but nothing i've found seems to work, such as putting DAEMON_OPTIONS(`Port=smtp,Addr=127.0.0.1, Name=MTA') in sendmail-slackware.mc and recompiling.
The way to configure Sendmail to listen on a specific address and port number is with the DaemonPortOptions in the sendmail.cf file:
# SMTP daemon options
o DaemonPortOptions=Addr=127.0.0.1,Port=smtp,Name=MTA
The configuration line you see here forces Sendmail to listen on the smtp port (usually 25/tcp as defined in /etc/services) on the loopback interface (address 127.0.0.1).
If you prefer, you may also set this option in your m4 macro configuration file. If you are using Sendmail v8.11 or later, then use the following configuration directive:
Since I have no experience of mail servers and you clearly have waaaay more than me :), do you think you can explain this to me?
If you disable external listening of port 25, doesn't that mean people can't e-mail you?
If I mailed your address, wouldn't I look up your domain, then connect to your port 25, which would then e-mail it to you? Or have I got something wrong :)?
Like I said, I am completely new to this sort of thing and have done very little research, I always thought you had to allow external clients to connect to port 25 but only allow them to e-mail your domain?
I did this. It was a while back so I hope I get it right.
I suspect that you are already firewalled, but want to clean up at the source, not just rely on the 'gatekeeper'?
The critical file in all this is /etc/mail/sendmail.cf but you cannot modify this file directly, you have to use m4, so make sure m4 is installed, it is currently m4-1.4.1-i486-1.
sendmail-slackware.mc will be the template which is copied to config.mc which in turn is compiled to generate a new /etc/mail/sendmail.cf!
back up /usr/share/sendmail/cf/cf/sendmail-slackware.mc
then edit it:
dnl# This is the default sendmail .mc file for Slackware. To generate
dnl# the sendmail.cf file from this (perhaps after making some changes),
dnl# use the m4 files in /usr/share/sendmail/cf like this:
dnl#
dnl# cp sendmail-slackware.mc /usr/share/sendmail/cf/config.mc
dnl# cd /usr/share/sendmail/cf
dnl# sh Build config.cf
dnl#
dnl# You may then install the resulting .cf file:
dnl# cp config.cf /etc/mail/sendmail.cf
dnl#
include(`../m4/cf.m4')
VERSIONID(`default setup for Slackware Linux')dnl
OSTYPE(`linux')dnl
dnl# These settings help protect against people verifying email addresses
dnl# at your site in order to send you email that you probably don't want:
define(`confPRIVACY_FLAGS', `authwarnings,novrfy,noexpn,restrictqrun')dnl
dnl# Uncomment the line below to send outgoing mail through an external server:
dnl define(`SMART_HOST',`mailserver.example.com')
dnl# No timeout for ident:
define(`confTO_IDENT', `0')dnl
dnl# Enable the line below to use smrsh to restrict what sendmail can run:
dnl FEATURE(`smrsh',`/usr/sbin/smrsh')dnl
dnl# See the README in /usr/share/sendmail/cf for a ton of information on
dnl# how these options work:
FEATURE(`use_cw_file')dnl
FEATURE(`use_ct_file')dnl
FEATURE(`mailertable',`hash -o /etc/mail/mailertable.db')dnl
FEATURE(`virtusertable',`hash -o /etc/mail/virtusertable.db')dnl
FEATURE(`access_db', `hash -T<TMPF> /etc/mail/access')dnl
FEATURE(`blacklist_recipients')dnl
FEATURE(`local_procmail',`',`procmail -t -Y -a $h -d $u')dnl
FEATURE(`always_add_domain')dnl
FEATURE(`redirect')dnl
dnl# Toby starts here
dnl Don't create a default MSA configuration
FEATURE(`no_default_msa')dnl
dnl Limit the MSA to the loopback address
DAEMON_OPTIONS(`Name=MSA, Port=587, Addr=127.0.0.1, M=E')dnl
dnl Limit the MTA to the 127.0.0.1 interface
DAEMON_OPTIONS(`Name=MTA, Addr=127.0.0.1')dnl
dnl#Toby ends here
dnl# Turn this feature on if you don't always have DNS, or enjoy junk mail:
dnl FEATURE(`accept_unresolvable_domains')dnl
EXPOSED_USER(`root')dnl
dnl# Also accept mail for localhost.localdomain:
LOCAL_DOMAIN(`localhost.localdomain')dnl
MAILER(local)dnl
MAILER(smtp)dnl
MAILER(procmail)dnl
see the new lines between dnl# Toby starts here - dnl#Toby ends here ??
now if you want you can keep an eye out for errors, open up a console and type
tail -f /var/log/maillog
then
cd /usr/share/sendmail/cf/cf
cp sendmail-slackware.mc config.mc
m4 /usr/share/sendmail/cf/m4/cf.m4 config.mc > /etc/mail/sendmail.cf
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