Sendmail - open relay.

[Mark Harshman_1]

We are trying to activate an open mail relay on one server, to out snmp server. We are not sure what ruleset gets activated for an open relay. Our intent here is to forward from specific domains behind our firewall (we're aware of the no-no's for using open relay). My question is basically, the proper confuration needed for the .cf file. How does this interact with the smart relay? or does it? Thanks in advance.

[Steven E. Protter · Accepted solution]

Relay is handled for sendmail in /etc/mail/access file

hostnmae RELAY


or

IP_ADDRESS RELAY


This is a tab delimited data file. In later versions of sendmail a script called gen_cf will put this into production.

This allows relay.

You will probably need entries to validate the domains as well.

/etc/mail/virtusertable
/etc/mail/genericstable

Same basic formats.

@domain.com localuser
@domain.com remoteuser@server.domain.com
user@domain.net localuser2

tab delimited
gen_cf puts it into production

genericstable is reverse format with th user before the domain.

SEP

[Brian Bergstrand]

For sendmail 8.9 or les:

Check out the LocalIP and LocalNames directives in sendmail.cf. If you enable these files, and then create them in /etc/mail, the addresses listed in the files will be able to relay through your server.

For Sendmail 8.10 and above:

Use the file /etc/mail/relay-domains for the same effect as above.

HTH.