[SOLVED] Sendmail - how to configure LAN-only messaging

Today, my ISP (Time-Warner/Spectrum) went down for some kind of maintenance and will be for several hours. However, I still need the various hosts on my LAN to be able to exchange email. The main 'server' on the LAN has local IP 192.168.0.15 and the router directs public domain resolutions of mydom.com to this internal address.

Another host on the LAN, 'hpmini', has sendmail.cf configured to use mydom.com as the SMART_HOST, and the 192.168.0.15 host has "92.168.0 RELAY" set in /etc/mail/access.

All that works just fine. 'hpmimi' can send mail to recipients on 'server' ... until the ISP goes down and mydom.com is no longer resolvable.

Even with the ISP down, LAN hosts can still see each other either by explicit IP or by hostname (the router acts as a local DNS server). I want to fix things so mail can be delivered between LAN hosts, even if there is not ISP working to resolve public domain names.

I've tried changing the .mc file on 'hpmini' (192.168.0.10) to:

define(`SMART_HOST',`[192.168.0.15]')dnl
dnl# MASQUERADE_AS(`mydom.com')
dnl# FEATURE(`masquerade_envelope')
dnl# FEATURE(`masquerade_entire_domain')

I.e. changing the SMART_HOST to the explicit IP address and commenting out the masquerade settings, but sending a message from 'hpmini' (192.168.0.10) to 'server' (192.168.0.15) fails with the following message on server's maillog:

Aug 15 11:17:10 server sm-mta[13609]: v7FFEn17013609: ruleset=check_rcpt, arg1=<mfoley@192.168.0.15>, relay=[192.168.0.10], reject=451 4.1.8 Domain of sender address root@hpmini.ALLUNEEDIZLUV does not resolve
Aug 15 11:17:10 server sm-mta[13609]: v7FFEn17013609: from=<root@hpmini.ALLUNEEDIZLUV>, size=669, class=0, nrcpts=0, proto=ESMTPS, daemon=MTA, relay=[192.168.0.10]

ALLUNEEDIZLUV is the "domain name" of my LAN. The messages are received on server, but rejected because the domain does not resolve.

How could I fix this? Could I put ALLUNEEDIZLUV in /etc/domaintable or /etc/local-host-table?

Greetings,

Well, from what it sounds like, all you need is an entry (READ: alias) in /etc/hosts on the mail server for the systems on your LAN that you want to appear as being in the domain.

You can take a look at this LQ-Wiki page for info on /etc/hosts and what you can do with it.

HTH. Let us know.

Thanks for that tip. That almost worked. I set 'server' (192.168.0.15) /etc/hosts to:

192.168.0.10            hpmini.ALLUNEEDIZLUV lincoln watcher

adding the underlined entry. When I sent a message from 'root@hpmini' to mfoley@server' it worked better, but I got:

Aug 16 00:27:39 server sm-mta[21549]: STARTTLS=server, relay=hpmini.ALLUNEEDIZLUV [192.168.0.10], version=TLSv1.2, verify=NO, cipher=DHE-RSA-AES256-GCM-SHA384, bits=256/256
Aug 16 00:27:39 server sm-mta[21549]: v7G4RcEv021549: from=<root@hpmini.ALLUNEEDIZLUV>, size=673, class=0, nrcpts=1, msgid=<201708160427.v7G4RbFe009599@hpmini.ALLUNEEDIZLUV>, proto=ESMTPS, daemon=MTA, relay=hpmini.ALLUNEEDIZLUV [192.168.0.10]
Aug 16 00:27:39 server sm-mta[21552]: v7G4RcEv021549: to=<mfoley@server.ALLUNEEDIZLUV>, delay=00:00:00, xdelay=00:00:00, mailer=relay, pri=120673, relay=mail.twc.com [107.14.73.68], dsn=5.0.0, stat=Service unavailable
Aug 16 00:27:39 server sm-mta[21552]: v7G4RcEv021549: v7G4RdEu021552: DSN: Service unavailable
Aug 16 00:27:39 server sm-mta[21552]: v7G4RdEu021552: to=<root@hpmini.ALLUNEEDIZLUV>, delay=00:00:00, xdelay=00:00:00, mailer=relay, pri=31988, relay=mail.twc.com, dsn=5.1.8, stat=Service unavailable

So, I added the following to /etc/mail/local-host-names

server.ALLUNEEDIZLUV

That worked! Note that leaving off "server." in this line did not work.

I'll play with this some more to verify, but I think that might be the solution.