Difference between revisions of "Email relay"

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[[Category:Linux]]
 
[[Category:Linux]]
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=Principle=
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Our server will forward all emails to another SMTP server. The SMTP server we're gonna install is stupid: only local domain, no account checking, no anti-virus or spam protection.
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# From a local point of view, all emails are send using Linux default configuration and system users
 +
# From the other hand - the big SMTP server ("Gmail", "Outlook", ...) - all emails come from the same account
 +
 +
 +
Principle:
 +
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[[File:SMTP server relay.png|none|SMTP server relay]]
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 +
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As you can see, POSTFIX SMTP server will just act as a proxy between local services and Gmail.
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=When to use it ?=
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If you only have a single server and want to monitor it, then use a relay! That's much easier than setup a complete email server. It's also easier to maintain!
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=Installation=
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<syntaxhighlight lang="bash">
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apt-get install postfix mailutils libsasl2-2 ca-certificates libsasl2-modules
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</syntaxhighlight>
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Choose:
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* Internet Site
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* Type your FQDN like: dev.daxiongmao.eu  ||  smartcard-gw.smartcards.vehco.com
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 +
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=Configuration=
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==POSTFIX global conf==
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Edit Postfix configuration
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<syntaxhighlight lang="bash">
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vim /etc/postfix/main.cf
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</syntaxhighlight>
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 +
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Add / adjust the SMTP relay and SASL settings (~ line 37)
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 +
<syntaxhighlight lang="bash">
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## SMTP relay
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relayhost = [smtp.gmail.com]:587
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smtp_sasl_auth_enable = yes
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smtp_sasl_password_maps = hash:/etc/postfix/sasl_password
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smtp_sasl_security_options = noanonymous
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smtp_sasl_tls_security_options = noanonymous
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smtp_tls_policy_maps = hash:/etc/postfix/tls_policy
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</syntaxhighlight>
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Do not change the default TLS settings !!
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==Credentials file==
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Create login / password file
 +
 +
<syntaxhighlight lang="bash">
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vim /etc/postfix/sasl_password
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</syntaxhighlight>
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Put the following content
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<syntaxhighlight lang="bash">
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[smtp.gmail.com]:587    USERNAME@gmail.com:PASSWORD
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</syntaxhighlight>
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Compute new hash for postfix
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<syntaxhighlight lang="bash">
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postmap /etc/postfix/sasl_password
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</syntaxhighlight>
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==TLS policy==
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Create TLS policy file
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<syntaxhighlight lang="bash">
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vim /etc/postfix/tls_policy
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</syntaxhighlight>
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 +
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Put the following content
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<syntaxhighlight lang="bash">
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[smtp.gmail.com]:587 encrypt
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</syntaxhighlight>
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 +
 +
Compute new hash for postfix
 +
 +
<syntaxhighlight lang="bash">
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postmap /etc/postfix/tls_policy
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</syntaxhighlight>
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==Apply changes==
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You must restart POSTFIX to apply changes
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 +
<syntaxhighlight lang="bash">
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service postfix restart
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/etc/init.d/postfix/reload
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</syntaxhighlight>
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=Test your configuration=
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<syntaxhighlight lang="bash">
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echo "Test from my new SMTP relay" | mail -s "Test Postfix SMTP relay" target@domain.com
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## Multi-users
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echo "Test from my new SMTP relay" | mail -s "Test Postfix SMTP relay" target@domain.com,target2@domain.com
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</syntaxhighlight>
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Check your logs!! <code>cat /var/log/syslog</code>
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=Configure aliases=
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To send all email address to "root" to your particular address you must create some aliases.
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 +
<syntaxhighlight lang="bash">
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vim /etc/aliases
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</syntaxhighlight>
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Put something like:
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<syntaxhighlight lang="bash">
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# See man 5 aliases for format
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postmaster:    root
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root:          me@mydomain.lu, you@mydomain.lu
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</syntaxhighlight>
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 +
Apply changes:
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<syntaxhighlight lang="bash">
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# Apply aliases to all the system
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newaliases
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# Restart postfix
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service postfix restart
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/etc/init.d/postfix/reload
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</syntaxhighlight>
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 +
 +
 +
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=Test your aliases=
 +
 +
<syntaxhighlight lang="bash">
 +
echo "Test from my new SMTP relay" | mail -s "Test Postfix SMTP relay" root
 +
</syntaxhighlight>
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 +
 +
 +
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=Usage=
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The usage is transparent.
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A lot of services like Zabbix, Nagios, Webmin... are already using the "mail" application. So you don't need to do anything on your side! :-)

Latest revision as of 11:52, 21 January 2017


Principle

Our server will forward all emails to another SMTP server. The SMTP server we're gonna install is stupid: only local domain, no account checking, no anti-virus or spam protection.

  1. From a local point of view, all emails are send using Linux default configuration and system users
  2. From the other hand - the big SMTP server ("Gmail", "Outlook", ...) - all emails come from the same account


Principle:

SMTP server relay


As you can see, POSTFIX SMTP server will just act as a proxy between local services and Gmail.



When to use it ?

If you only have a single server and want to monitor it, then use a relay! That's much easier than setup a complete email server. It's also easier to maintain!



Installation

apt-get install postfix mailutils libsasl2-2 ca-certificates libsasl2-modules

Choose:

  • Internet Site
  • Type your FQDN like: dev.daxiongmao.eu || smartcard-gw.smartcards.vehco.com



Configuration

POSTFIX global conf

Edit Postfix configuration 

vim /etc/postfix/main.cf


Add / adjust the SMTP relay and SASL settings (~ line 37) 

## SMTP relay 
relayhost = [smtp.gmail.com]:587
smtp_sasl_auth_enable = yes
smtp_sasl_password_maps = hash:/etc/postfix/sasl_password
smtp_sasl_security_options = noanonymous
smtp_sasl_tls_security_options = noanonymous
smtp_tls_policy_maps = hash:/etc/postfix/tls_policy


Do not change the default TLS settings !!


Credentials file

Create login / password file 

vim /etc/postfix/sasl_password


Put the following content 

[smtp.gmail.com]:587    USERNAME@gmail.com:PASSWORD


Compute new hash for postfix 

postmap /etc/postfix/sasl_password


TLS policy

Create TLS policy file 

vim /etc/postfix/tls_policy


Put the following content 

[smtp.gmail.com]:587 encrypt


Compute new hash for postfix 

postmap /etc/postfix/tls_policy


Apply changes

You must restart POSTFIX to apply changes 

service postfix restart
/etc/init.d/postfix/reload



Test your configuration

echo "Test from my new SMTP relay" | mail -s "Test Postfix SMTP relay" target@domain.com

## Multi-users
echo "Test from my new SMTP relay" | mail -s "Test Postfix SMTP relay" target@domain.com,target2@domain.com


Check your logs!! cat /var/log/syslog



Configure aliases

To send all email address to "root" to your particular address you must create some aliases. 

vim /etc/aliases

Put something like: 

# See man 5 aliases for format
postmaster:    root
root:          me@mydomain.lu, you@mydomain.lu

Apply changes: 

# Apply aliases to all the system
newaliases

# Restart postfix
service postfix restart
/etc/init.d/postfix/reload



Test your aliases

echo "Test from my new SMTP relay" | mail -s "Test Postfix SMTP relay" root



Usage

The usage is transparent.

A lot of services like Zabbix, Nagios, Webmin... are already using the "mail" application. So you don't need to do anything on your side! :-)

Retrieved from "http://www.daxiongmao.eu/wiki/index.php?title=Email_relay&oldid=2754"