question about sendmail

[Bill Hacker]

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