Re: question about sendmail

[Bill Hacker <wbh@xxxxxxxxxxxxx>]

Saverio Iacovelli wrote:

> After the installation, DFly OS have got a active
> sendmail server.
> 1) Does it need to configure a DNS server for sending
> email with mail client and sendmail?

Sendmail (any MTA) will ordinarily follow the internet 'food chain' to find a DNS.

You need not run one locally, though a properly implemented one may speed-up the 
smtp process.

> 2) Can sendmail works in indipendent way from DNS
> server?

An MTA (Exim, anyway... no longer 'current' with sendmail here) can be set up to 
do 'local' (on-box) delivery, and 'nearby' private servers such as needed for 
chron'ed reports, by relying just on the ~etc/hosts file entries and to the 'net 
at large with 'domain literals', ie:

<a validuser>@<some valid IP>

- which may be all you need for LAN or 'private' testing w/o risk of polluting 
the 'net, and is the only way to reach boxen that have no published <domain>.<tld>.

A DNS query is not used just for routing outbound, but also for verification of 
incoming in a number of places in 'aware' MTA's - Exim especially.

In general:

~/etc/rc.conf  needs a defaultrouter entry

~/etc/hosts must at least not 'short-circuit' the routing

~/etc/resolv.conf must have a useful way of finding one or more nameservers.

manpages have more detail .....

HTH,

Bill