Re: Why DNS request ?

RICCARDO <castellani.riccardo@xxxxxxxxxx> wrote:

I'm using internel Linux mail server (RIC) with sendmail-8.12.10-1.1.1
as MTA and I have this domain: "example"; this domain is divided into
another 2 subdomains:
"east.example.com" , "west.example.com".
RIC server uses another mail server as "smart_host" which is on both
public network and internal network (it has 2 network card) to send
mail to external domain.
RIC server uses also mailertable mechanism to redirect messages to
another "SRV" mail server (with recipient domain "west.example.com")
while it handles directly users for "east.example.com" domain.
I don't understand because there is DNS request (record A) every time
I send email to any recipient domain (both example.com and others
domains); email is always redirected to either "smart_host" or "SRV"
mail server, but why it's necessary to do DNS request ?
My opinion is this work should have be executed from smart_host or SRV
server !!!

For host names used as smart relay or in mailertable:
sendmail looks first for MX record unless you put the name in square
brackets ([hostname]).

Sendmail also may do DNS lookup for addresses mentioned in:
* envelope sender address ("MAIL FROM:" in SMTP session)
to reduce risk of getting "undeliverable bounces"
* addresses in "To:" and "From:" headers
to rewrite CNAME names

--
[pl>en: Andrew] Andrzej Adam Filip : anfi@xxxxxxxxxxxx : anfi@xxxxxxxx
Open-Sendmail: http://open-sendmail.sourceforge.net/
There is no cure for birth and death other than to enjoy the interval.
-- George Santayana
.

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