I recently built a server and then tried to do a mail test and it worked inspite of no config changes, just installation of Postfix package and service up. Below are my doubts and

1. Does Linux client server require no config in order to send mail to email account present in the domain or to different domain as I was able to send test mail without any client config changes.
2. What working principle is behind this.
3. Does the same rule apply for sendmail.

Below is the config of postfix

[root@efeqw12~]# postconf -n
alias_database = hash:/etc/aliases
alias_maps = hash:/etc/aliases
command_directory = /usr/sbin
config_directory = /etc/postfix
daemon_directory = /usr/libexec/postfix
data_directory = /var/lib/postfix
debug_peer_level = 2
html_directory = no
inet_interfaces = localhost
inet_protocols = all
mail_owner = postfix
mailq_path = /usr/bin/mailq.postfix
manpage_directory = /usr/share/man
mydestination = $myhostname, localhost.$mydomain, localhost
newaliases_path = /usr/bin/newaliases.postfix
queue_directory = /var/spool/postfix
readme_directory = /usr/share/doc/postfix-2.6.6/README_FILES
sample_directory = /usr/share/doc/postfix-2.6.6/samples
sendmail_path = /usr/sbin/sendmail.postfix
setgid_group = postdrop
unknown_local_recipient_reject_code = 550

This is now your SEVENTH YEAR here. Along with your 'certification', these questions make zero sense. Anyone with that much experience knows:

1. That your mail client needs *SOME* configuration to send mail
2. The 'principle' is called a relay host/smart host.
3. And that ANY mail server uses these terms

And AGAIN as you've been asked numerous times in the past, you need to provide actual DETAILS. Saying "built a server" and "do a mail test" tells us nothing...you say zero about your environment, what kind of server (version/distro of Linux?) what you did/used to perform this mail test, etc. There could be any number of things in play here...along with sendmail running on your host now, and your installation of postfix isn't started and therefore, has no bearing on this test. What do you even mean by "linux client server"??
No, this is not the 'config of postfix'....had you read the man page on postconf, you'd see what the -n flag does.

I knew it, you would respond. I guess you don't like people asking doubts and concern over different forums. If the thread is in Redhat category then definitely the distro belongs in the same, and don't try to stand as a wall and do moral policing by saying what to ask and what to not. Who the hell are you to question me. I have raised doubts/question because I have those during trying to learn something unlike you which is always sulking and teaching everyone ethics to post question. Get lost and ignore the question if you don't want to answer.

Doesn't matter to me who asks what, where. I have no idea where else you posted this and frankly, don't care. I responded to what was posted here. Also, you need to look up the word "doubt" and the word "question"...they mean different things.
Where, exactly, did anyone say what to do and what not? Because it's Red Hat what does that tell us? RHEL WHAT??? 4? 5? 6? 7? Lots of options aren't there? Version of postfix? Installed from source or package???? DETAILS.
You were answered, and if you don't like the answer, that's too bad. You didn't provide details or ask a clear question....still, despite being here for seven years, and being told/asked to MANY times by MANY people.

You were asked for details:

• Version of RHEL
• Version of Postfix
• How you ran the test
• What you meant by "linux client server"
• Environment this is in (such as, LAN? WAN? Lab?), what the upstream mail server is, etc?

Don't want to answer? Then your 'certification' can tell you how to proceed. If you're actually trying to learn, then SHOW THAT EFFORT...answer questions and participate in the conversation, and apply what you've been told in the past. If you keep getting told to provide details, and DO NOT DO IT, you're not actually learning are you???

EDIT: Folks have been asking you for details for well over a year now...and last year, you were playing the "newbie" card to get a script:
http://www.linuxquestions.org/questi...9/#post5383627

...claiming that your RHCE didn't cover scripting (it does), and that you had a 'break' in your Linux career.

2 members found this post helpful.

This might help clarify how postfix sends mail, I know it helped me: http://superuser.com/questions/13746...ct-to-the-targ

Let me make it clear that any LQ member is free to post questions anywhere else, period. Now if that's an efficient way of pursuing things is another matter and one I won't comment on.


LQ is a friendly place for all things Linux (or rather UNIX) where people with different backgrounds and expertise share knowledge and help each other. LQ members must adhere to the LQ Rules, follow Netiquette and use common sense or else things can get not so friendly. If you feel irritation there are a lot of things you can do: outline in more detail what you've tried, provide technical information asked or ignore the person asking and move on.

So you see, saying "get lost" to a fellow LQ member is not what you want to do.
So please do not do that again.

I know I was harsh and rude. I was trying to get my doubts clears but then moral policing started and lecture started to pour in which did not help and I got it other away. I will stick to the rules of this forum.

Please, stop where you are. There was no "moral policing" or "lecture"...you have been asked for a LONG time now to provide details when asking a question. Unless you do, how do you think anyone, anywhere, can help? And it was ONE POST...how is that 'pouring in'???? Also, you asked 3 very simple, obvious questions that were answered, and which someone with 7 years experience should have already known. What actually "got it other way", is you not answering questions, and acting poorly. You CANNOT claim to be "trying to learn something", then ignore everything you've been told/asked previously.

If you want help, then answer the questions you've been asked You were asked for details:

• Version of RHEL
• Version of Postfix
• How did you install postfix? Package or source?
• How you ran the test
• What you meant by "linux client server"
• Environment this is in (such as, LAN? WAN? Lab?), what the upstream mail server is, etc?
• Is sendmail running?
• Was this EVER working, or is this a new issue?

Simple things, and many are the same from your other threads. Either answer, or there is no point in posting...we aren't going to guess as to your configuration. And since you have a 'certification' and 7 years experience, and you say you're using some version of RHEL...have you called Red Hat support, since you are PAYING FOR RHEL, RIGHT???

Also, again...the word "doubts" and the word "questions" mean different things.

The question was not meant to a specific configuration or any issue. I was trying to understand how postfix/sendmail work in the background, not that I was asking to help me build the service. And second thing does it mean that a person who registered in 2009 out of curiosity and joined this forum does not mean that he started the same day to work on linux. I have many times told in the past that I became active linux user from last 2.5 yrs and you can refer each of the post where you kept saying 7 yrs of experience and all. Yes I do have certification and as per my job profile I don't get to implement each and every stuff of linux on a daily basis, So whenever I have doubts or need some clarification I come here but instead it turns out to be a complete fail. And regarding redhat support, Yes I did raised a case with them and they said it will work with by default configuration and will be able to send mail, this made me confused and I asked question here. I think I should put this forum logins to rest and should look for answers/dobuts/question/clarification somewhere else

Oh? In your first post in this thread:
...which certainly seems to say that you were/are talking about a specific server and issue, and you were asking for advice on how the service works. Those three simple questions were answered in the first reply. No one said you were asking for help on building a service.
Really?? Because putting your user name and "Linux" into Google pulls up a LinkedIn profile that says you have 6.5 years experience with ZERO gaps, starting in 2009. When you registered here.
https://www.linkedin.com/in/chetan-s...?trk=pub-pbmap
Because you DON'T PROVIDE DETAILS, and get nasty when you're asked for them.
And back to "you don't provide details"....if you already asked RHEL support, don't you think that would have been a good thing to mention? Makes the question better, doesn't it??? Also, this makes zero sense, given you started this post by saying you weren't asking about a specific server, or specific configuration....so how did you open a case on a server that didn't exist?

Again...it needs SOME configuration somewhere. Which goes back to all the questions you were asked previously, and still haven't answered. To spoon-feed you the REASONS for such questions:

• You don't need a smarthost if mailertable is already defined, and has a second hop
• If you ran the test with mailx, that ALSO can have a next-hop configured, negating the need for mail services configuration AT ALL
• If sendmail is up/running/configured to SEND, then THAT service may be doing what you THINK postfix is doing.
• If you ran the test with some other program, then THAT may have a configuration of its own

See why details are important??? Those are just a FEW of the things that it may be....but, you won't answer questions when asked, or EVER provide details. Still don't....so don't wonder why when you go to another forum and ask questions (not "doubts"), that THEY will ask you for details as well. Be sure you are as nasty with them as you were here, and see what kind of answers you get.

Profile says Linux admin but not the exact kind of work I used to do. Indeed I was part of it, just on the designation and when I did not get chance to work on core stuff, I started self learning and move to in 2014 when I did my certificate. It was kind of on/off but not totally deep into it and I guess I have told you all these in 2014 when I started working actively in Linux, So I am not a liar or trying to get some shortcut to do some stuff.

Coming to question which I asked

1. OS version - RHEL 6.4
2. Sendmail package - sendmail-8.14.4-8.el6.x86_64
sendmail-cf-8.14.4-8.el6.noarch
Version 8.14.4
3. I initiated a test mail without defining relay in /etc/mail/submit.mc or smarthost in /etc/mail/sendmail.mc
4. mail -s "Test" testid@network.lab and I was able to receive the mail on the id - testid@network.lab in outlook
5. I wanted to understand how it worked, does SMTP take the " @network.lab " and then go to system DNS record in /etc/resolve.conf and which then contact MX record of doman(network.test) and then SMTP communicate with it and send mail to recipient address.

If you weren't a Linux admin, then don't call yourself one on your resume. Either you're lying on your resume/Linkedin profile, or here. They both can't be true.
...and going back to your VERY FIRST POST, and the title of this thread, you said POSTFIX....NOT SENDMAIL. You also said that this thread wasn't asking about a specific configuration...which contradicts your first post, and post #10, where you specifically said "The question was not meant to a specific configuration or any issue." Again...either you have a real system with real issue/question or you don't...they both can't be true.

The two are very different. And was this a new installation? Old server? Again, was there EVER mail working on that system? Because, as said previously, these things MATTER. You could have a mailertable database...is there one? What is the mail binary linked to?? Sometimes it's linked to mailx..which could easily read a .mailrc file in your home directory, regardless of what mail system you have defined/installed/started.

Mail doesn't look up anything based on a domain name...unless you tell it to (see previous few comments about mailertable.db, .mailrc, etc.), which you still haven't told us about, despite them being mentioned several times now. SMTP needs some way of knowing how to communicate...much like a web browser, you can't just put in "http" on the command line, and have it resolve a domain and somehow communicate...you need some client piece on the local end to use that protocol. According to the RHEL documentation, POSTFIX is installed by default, and sendmail is deprecated. So again...if you already had postfix up and running on this system, and just LOADED sendmail, your system is still using what was installed/configured to send messages.

Again, very obviously...unless you have something to work with the protocol, it's not going to work, period. This goes for email, web, SNMP, or anything else you can name.

I am not that stupid to check if there are any existing mail services(postfix) installed on the machine or not before installing sendmail/postifx. I know that RHEL comes with postfix by default but I did not choose that package during the build process of this new server. Secondly I did not lied any where in my profile, I said the designation was given as Linux so I kept that but I was handling several things and bit of Linux too. I don't think this post is going anywhere apart from the argument. I will try to explore some other option to get my doubts clear.

Again...we do not, and CAN NOT, know what you've done/checked until you TELL US. You asked for advice, and now you get nasty about "I am not that stupid".
So again...which is it? You say "sendmail/postfix"...which did you install, because at this point, you've said both. And again, you initially said new server, then said it was it was "not a specific configuration". So you now say you installed sendmail...great. So again, as you've been asked:
Is there a mailertable.db file? Anything defined? And again, as you've been asked. is this a NEW server, and was mail EVER WORKING ON IT in the past?
...except for the part where you said you have 6.5 years of experience in one place, and then claim 2.5 years here. Again, both can't be true.
AGAIN...the word is "QUESTIONS" not DOUBTS...they mean different things.

Your questions were answered in the last post. Did you not read/understand them?? And again...someone with a 'certification' should know how network services work.