Obsidian/05.02 Networks/Configuring Postfix.md

Alias	Tag	Date	DocType	Hierarchy	TimeStamp	location	CollapseMetaTable
Postfix	🖥️ 📧	2021-09-10	Personal	NonRoot		51.514678599999996 -0.18378583926867909	true

Parent:: Selfhosting, Server Alias, Server Cloud, Server Tools, Server VPN

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Configuring Postfix

 

title: Summary
collapse: open
This note goes through the installation of Postfix, an email-handling solution for servers.

 

style: number

 

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Installation

#^Top  

Installation is simple and opens a dialogue box. Steps are described below:

1. Install Postfix

~~~bash
sudo apt-get install -y postfix postfix-pgsql -y
~~~

2. Configuration screen

Choose 'Internet Site'

3. System mail name

Define a name and make a note of it for further use.

 

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Generic configuration

#^Top  

title: Documentation
[Basic config](https://github.com/simple-login/app)

The basic configuration is run in detail below.

 

Main.cf

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/etc/postfix/main.cf

Edit the file whilst editing the following values:

1. myhostname (current server)
2. mydomain (associated domain)
3. my origin (associated domain)

title: main.cf
~~~bash
 ###### POSTFIX config file, adapted for SimpleLogin
smtpd_banner = $myhostname ESMTP $mail_name (Ubuntu)
biff = no

###### appending .domain is the MUA's job.
append_dot_mydomain = no

###### Uncomment the next line to generate "delayed mail" warnings
######## delay_warning_time = 4h

readme_directory = no

###### See http://www.postfix.org/COMPATIBILITY_README.html -- default to 2 on fresh installs.
compatibility_level = 2

###### TLS parameters
smtpd_tls_cert_file=/etc/ssl/certs/ssl-cert-snakeoil.pem
smtpd_tls_key_file=/etc/ssl/private/ssl-cert-snakeoil.key
smtpd_tls_session_cache_database = btree:${data_directory}/smtpd_scache
smtp_tls_session_cache_database = btree:${data_directory}/smtp_scache
smtp_tls_security_level = may
smtpd_tls_security_level = may

###### See /usr/share/doc/postfix/TLS_README.gz in the postfix-doc package for
###### information on enabling SSL in the smtp client.

alias_maps = hash:/etc/aliases
mynetworks = 127.0.0.0/8 [::ffff:127.0.0.0]/104 [::1]/128 240.0.0.0/24

###### Set your domain here
mydestination =
myhostname = app.mydomain.com
mydomain = mydomain.com
myorigin = mydomain.com

relay_domains = pgsql:/etc/postfix/pgsql-relay-domains.cf
transport_maps = pgsql:/etc/postfix/pgsql-transport-maps.cf

###### HELO restrictions
smtpd_delay_reject = yes
smtpd_helo_required = yes
smtpd_helo_restrictions =
    permit_mynetworks,
    reject_non_fqdn_helo_hostname,
    reject_invalid_helo_hostname,
    permit

###### Sender restrictions:
smtpd_sender_restrictions =
    permit_mynetworks,
    reject_non_fqdn_sender,
    reject_unknown_sender_domain,
    permit

###### Recipient restrictions:
smtpd_recipient_restrictions =
   reject_unauth_pipelining,
   reject_non_fqdn_recipient,
   reject_unknown_recipient_domain,
   permit_mynetworks,
   reject_unauth_destination,
   reject_rbl_client zen.spamhaus.org,
   reject_rbl_client bl.spamcop.net,
   permit
~~~

 

relay domains

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/etc/postfix/pgsql-relay-domains.cf

Below is the default config for the file (replace mydomain.com with relevant value):

title: master.cf
~~~bash
###### postgres config
hosts = localhost
user = myuser
password = mypassword
dbname = simplelogin

query = SELECT domain FROM custom_domain WHERE domain='%s' AND verified=true
    UNION SELECT '%s' WHERE '%s' = 'mydomain.com' LIMIT 1;
~~~

 

transport maps

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/etc/postfix/pgsql-transport-maps.cf

Below is the standard declaration of the file (replace mydomain.com with the relevant value):

title: pgsql-transport-maps.cf
~~~bash
###### postgres config
hosts = localhost
user = myuser
password = mypassword
dbname = simplelogin

###### forward to smtp:127.0.0.1:20381 for custom domain AND email domain
query = SELECT 'smtp:127.0.0.1:20381' FROM custom_domain WHERE domain = '%s' AND verified=true
    UNION SELECT 'smtp:127.0.0.1:20381' WHERE '%s' = 'mydomain.com' LIMIT 1;
~~~

 

Generic commands

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Restart the service

~~~bash
sudo systemctl restart postfix
~~~

 

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Allow external connections

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title: Documentation
[Fwd to external smtp](https://github.com/simple-login/app/discussions/612)

 

Incoming

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Ports

Ports (25, 465, 587) need to be opened by the firewall:

~~~bash
sudo ufw allow (port)/tcp
~~~

 

Networks

#^Top Definition of permitted networks to restrict access (in Configuring Postfix#Main cf).

 

Submission/SMTPD

/etc/postfix/master.cf

Options are coded in the file by default. Uncheck necessary directives.

 

SSL cert

#^Top Postfix SSL certs need to match that of the server (in Configuring Postfix#Main cf).

 

SASL

#^Top Tutorial

 

Add SASL users

title: add a user
~~~bash
sudo saslpasswd2 -c -u (mydomain.tld) (username)
~~~

title: check number of users
~~~bash
sudo sasldblistusers2
~~~

 

Outgoing

Allow for connecting to an external SMTP - not tested.

 

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Monitor Postfix

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Monitor outgoing emails

Unfortunately there is no built-in functionality to monitor specifically outgoing emails. The following command can however be used and grans relevant info from mail.log:

~~~bash
sudo grep "status=sent" /var/log/mail.log | egrep -ve 'postfix/(cleanup|pickup|master|qmgr|smtpd|local|pipe)'
~~~

 

Monitor SMTP connections

~~~bash
sudo tail -f /var/log/mail.log
~~~

 

Identify IPs with Failed Logins

~~~bash
sudo grep " warning: " /var/log/mail.log |cut -d '[' -f3 |cut -d ']' -f1 |sort -u
~~~

 

And

 

~~~bash
sudo grep " reject: " /var/log/mail.log |cut -d '[' -f3 |cut -d ']' -f1 |sort -u
~~~

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