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Sendmail

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KapilRaj
Honored Contributor

Sendmail

All,

1. When i send an email to kaps@kapil.com , Is it a "MUST" that my local sendmail is capable of resolving the name (kapil.com)?.
2. Or is it ok if resolved at the Relay server ?.
3. What happens if it is not resolved at ,

a) local send mail
b) Relay Server
4. Can anybody explain how an email goes from kaps@ponl.com (from ponl.com) to kaps@kapil.com (kapil.com) ?. i.e. step by step.

Regds,

Kaps
Nothing is impossible
7 REPLIES
Jose Mosquera
Honored Contributor

Re: Sendmail

Hi,

If you have done reference appropriately about your smtp engine mail server (Relay Server) in /etc/mail/sendmail.cf:
DS

And is full reachable (ping ), then the trick is define your external domain (kapil.com) into your /etc/hosts file with the same IP address that your smtp engine mail server.i.e:
kapil.com

kapil.com resolution will be full reachable from your host (ping kapil.com)

Try a simple test from your box:
#echo "Test"|sendmail -v @kapil.com

BR.
KapilRaj
Honored Contributor

Re: Sendmail

bringing it to the TOP . I need more help
Nothing is impossible
Geoff Wild
Honored Contributor

Re: Sendmail

Sendmail relies on DNS.

So, out of the box, your local sendmail must be able to resolve - otherwise it won't send.

Though, you can set the DS macro in sendmail.cf to a "Smart Relay" server.


"Can anybody explain how an email goes from kaps@ponl.com (from ponl.com) to kaps@kapil.com (kapil.com) ?"

That depends - where email originates, how ponl.com is setup, etc.

If on the server for ponl.com, then it goes from there directly to the server @ kapil.com.

To test yourself, use sendmail on the commandline:

sendmail -v kaps@kapil.com

Rgds...Geoff
Proverbs 3:5,6 Trust in the Lord with all your heart and lean not on your own understanding; in all your ways acknowledge him, and he will make all your paths straight.
Christopher Caldwell
Honored Contributor

Re: Sendmail

It depends. If you're using rulesets that require resolution, you'll need to run a resolver. BTW, these days, there's almost no reason I can think of not to run a resolver. There's few reasons I can think of not to run a secured, caching only name server (most are security related).

As ealier posters suggested, it is possible for your host to hand a relay the mail without resolving the To: address, as long as it can resolve and/or connect to the relay.
Steven E. Protter
Exalted Contributor
Solution

Re: Sendmail

1. When i send an email to kaps@kapil.com , Is it a "MUST" that my local sendmail is capable of resolving the name (kapil.com)?.

No: You can use an email relay server. All you need is network connectivity to that server.


2. Or is it ok if resolved at the Relay server ?.

Yes

3. What happens if it is not resolved at ,

a) local send mail
b) Relay Server
4. Can anybody explain how an email goes from kaps@ponl.com (from ponl.com) to kaps@kapil.com (kapil.com) ?. i.e. step by step.

The mail goes into the mail queue. This can be displayed with the mailq command

sendmail -v -q

This will process the queue in verbose mode and show you how sendmail does the job.

Thats the best way to answer #4.

But.

In scenario 2, the mail is passed off to the relay server. So long as its accepted thats the end of it.

If sendmail has to handle the mta, its best to look at the process as follows:

sendmail -v -d8.99 -d38.99 someone@aol.com
type text

.


This will show you EVERY step sendmail takes in running the mail tranfer process.

SEP
Steven E Protter
Owner of ISN Corporation
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Naveej.K.A
Honored Contributor

Re: Sendmail

hi kapil,

My thoughts are this way!!!

1. its not must that the local sendmail program should be capable of resolving the name kapil.com, either your mailhub or your relay server should be capable. In this case, your local sendmail should be configured with a DS Macro to specify the Smart Relay host which inturn resolves the kapil.com domain.

2. Yes it is ok if it is resolved at the relay server.

3.
a)Its forwarded to the Smart Relay if it set, otherwise, it bounces back to user with a copy to the postmaster
b)It bounces back if its not resolvable. a copy comes to the postmaster too.

4. Internally, I mean within ponl.com and kapil.com it would depend upon how your mail routing is setup, i mean to say the relay hosts and other things like MX records (mail exchanger) through DNS. Once the mail comes from a PC wher kaps@ponl.com has his mail client and reaches the relaying server for ponl.com, it contacts the DNS (internet) or its own DNS if its setup in the ponl.com host and contacts kapil.com and pass on the mail...

Hope this helps kapil...Working in Night Shift!!!!

Naveej
practice makes a man perfect!!!
KapilRaj
Honored Contributor

Re: Sendmail

I asked the same question to some of my peers... they tried to explain the same.

What I understood is that, I have a better understanding out here in ITRC. I understand ITRC's language than of my peers.

Thank you so much.

Kaps
Nothing is impossible