SMTP: Configure a MTA to forward (relay) email through a smart host.

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In order to test this configuration, you will need to set up a DNS server and configure a central mail server (here at 192.168.1.1) to receive mails.

Remove the sendmail package (sendmail is more complicated to configure):

# yum erase sendmail

Install the postfix package:

# yum install -y postfix

Activate the postfix service at boot:

# chkconfig postfix on

Start the postfix service:

# service postfix start

Let’s assume that your local server is called server.example.com on the 192.168.1.0/24 network and your smart host (outgoing mail gateway) is at 192.168.1.1.
Edit the /etc/postfix/main.cf file and change the following directives:

myhostname = server.example.com
mydomain = example.com
myorigin = $mydomain
inet_interfaces = all
mydestination = $myhostname, localhost.$mydomain, localhost
mynetworks = 192.168.1.0/24, 127.0.0.0/8
relayhost = 192.168.1.1

Check the syntax:

# postfix check

Check the non-default configuration:

# postconf -n

Reload the postfix configuration:

# service postfix reload
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14 Comments on "SMTP: Configure a MTA to forward (relay) email through a smart host."

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papaand1
Member
papaand1

Hi,
thank you so much for those tutos, but here i am a little bit confused.
what’s the hostname or ip address for central mail server?
what’s the hostname or ip address for the smart host?
and the main.cf file in which host are we supposed to edit it?
thank a lot

papaand1
Member
papaand1

i got it. thank you

papaand1
Member
papaand1

HI,
I have one question for you. if i want to block a client with 192.168.1.20 for example to send email how am i going to proceed?
thank you

papaand1
Member
papaand1

thank you so much

TexasJosh
Member
TexasJosh

Hi,
I just stumbled upon this article when I searched postfix configuration file setups. I have a more general question here: do I have to have a private domain name and a private server name to be able to use your tutorial here? By the way, I don’t own a domain name and I don’t have a server at home. I can send email out through gmail relay only from command line, but not receive emails.
Thanks.

Lisenet
Member

Just to add something, you do not have to have a private domain nor a private server to be able to use the tutorial, if you send emails from the computer where the Postfix server is configured, and relay to your Gmail mailbox.

For example, this tutorial would work on your laptop if you were to install Postfix on it and configure relay to your Gmail account. You would be able to send emails from your PC to Gmail via Postfix. It is not clear on what exactly you want to achieve here, therefore more details would be helpful.

TexasJosh
Member
TexasJosh
I think the author has answered my question. Thanks. This is a common issue with the online posting without editors looking over for kosherness. There are lots of hidden assumptions on these tutorials not known to a laymen, but obvious to the author. Say for example, the author could at the beginning of the tutorial state that this tutorial is to show you how to setup Linux to send and receive emails on command line using a Linux app called postfix. But to be able to receive and read email on command line, you must own a domain name (fee-based)… Read more »
Sam
Member
Sam

Just a thought, to read the emails, through gmail, is the setting correct through the encryption / 2 factor authentication. I imagine this can be difficult.

Lisenet
Member
I think that the content of this blog post reflects the heading “Configure a MTA to forward (relay) email through a smart host” perfectly. What I’m saying is that the article is about configuring an MTA to forward emails. I understand that you may be interested in a configuration which allows you to receive emails, however, this was never the scope of the article. Now, you expressed concerns that to be able to receive and read email on a command line, you must own a domain name (fee-based) and a server (purchased). This is incorrect. You can receive and read… Read more »
Lisenet
Member

If you use Gmail, then Postfix works as a relay. Your mailbox is hosted on Gmail. When an email “comes back”, it goes to Gmail, not Postfix. To be able to retrieve incoming GMAIL messages you need a POP/IMAP client, but not Postfix.

You can configure all the above on your computer without having to purchase a single domain or to buy a server. However, if you don’t want Gmail but prefer to host your own email server, then yes, you need to have a domain and a place to run it. I hope this clarifies things.

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RHCSA7: Task of the day

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Archive and compress the content of the /opt directory (create files if none exists).
Uncompress and unarchive the resulting file in /root

RHCE7: Task of the day

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Set up a caching-only DNS server.

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