Setting up a mail server on a Linux system is useful for hosting email for a domain name, or even just to have local email capabilities. Local email in itself is a convenient feature on a machine used by many users, and even if there is no such traffic, many services dump their reports and messages into e-mails, which is delivered to the root user locally, so the sysadmin will be notified on any events of interest when they log in and switches to root user.
Sendmail: “unqualified hostname unknown; sleeping for retry unqualified hostname
If you have configured Sendmail on your Linux system and are still unable to send emails because of a unqualified hostname
error, we have a few suggestions that you can use to try and remedy the issue.
Send an email using Telnet
In this guide, we’ll show the step by step instructions to send an email using Telnet on a Linux system. This a great way to test your mail server configuration such as exim, sendmail or postfix without the need for an email client.
In this tutorial you will learn:
- How to install Telnet on major Linux distros
- How to send an email using Telnet protocol on Linux
Configuring Gmail as a Sendmail email relay
Sendmail is email routing software that can allow Linux systems to send an email from the command line. This allows you to send email from your bash scripts, hosted website, or from command line using the mail
command. Another example where you can utilize this setting is for notification purposes such as failed backups, etc.
In this guide, we’ll go over the step by step instructions to configure Gmail as a relay for the sendmail client on Linux. Note that Sendmail is just one of many utilities which can be configured to rely on a Gmail account. Others that are capable of this include postfix, exim, ssmpt, etc. The instructions here should work for any mainstream Linux distribution.
In this tutorial you will learn:
- Gmail configuration prerequisites
- How to install Sendmail and mail utilities on Linux
- How to configure Gmail as a relay for Sendmail
- How to test the config by sending an email from command line
How to check domain’s MX ( mail exchange ) records using dig command on Linux
dig
command is a very useful DNS lookup utility. It can be used to retrieve DNS records information of any domain name by querying specifc DNS servers. It is also a great troubleshooting tool for any admin configuring or troubleshooting existing DNS server.
To retrieve domain MX records simply use MX
option in combination to domain name you wish to query. For example the below command will query MX records for google.com:
How to install, configure, and use mutt with a gmail account on Linux
Email reader programs such as Thunderbird or Evolution are great, but sometimes they can feel bloated. If you found yourself working mainly from CLI, you may find useful to learn how to install and configure Mutt, a command line email client: that’s what we will do in this tutorial.
In this tutorial you will learn:
- How to install Mutt
- How to configure Mutt to be used with a gmail account
- How to store sensitive information in an encrypted file and source it from the main Mutt configuration
- How to setup some macros to easily switch between mailbox directories
How to install Mailspring on Ubuntu 18.04 Bionic Beaver Linux
Objective
The objective is to install Mailspring on Ubuntu 18.04 Bionic Beaver Linux.
Operating System and Software Versions
- Operating System: – Ubuntu 18.04 Bionic Beaver Linux
Requirements
Privileged access to your Ubuntu System as root or via sudo
command is required.
Conventions
How to install Hiri on Ubuntu 18.04 Bionic Beaver Linux
Objective
The objective is to install Hiri on Ubuntu 18.04 Bionic Beaver Linux.
Operating System and Software Versions
- Operating System: – Ubuntu 18.04 Bionic Beaver Linux
Requirements
Privileged access to your Ubuntu System as root or via sudo
command is required.
Conventions
How to install Thunderbird on Ubuntu 18.04 Bionic Beaver Linux
Objective
The objective is to install Thunderbird on Ubuntu 18.04 Bionic Beaver Linux
Operating System and Software Versions
- Operating System: – Ubuntu 18.04 Bionic Beaver Linux
Requirements
Privileged access to your Ubuntu System as root or via sudo
command is required.
Conventions
How to install postfix mail server on RHEL 8 / CentOS 8
Postfix is a common mail server, many large distributions are shipped with Postfix installed by default. The default configuration allows local mailing only, but that in itself is very useful on a machine used by many users, and even if there is no such traffic, many services dump their reports and messages into e-mails, which is delivered to the root
user locally, so the sysadmin will be noticed on any events of interest when he/she logs in and switches to root
user.
A simple example would be scheduled cron
jobs: any output not redirected from the output of a script running from cron will be wrapped to an e-mail and will be delivered to root
‘s mailbox, so the administrator does not even have to make any effort to have the reports of the nightly backup jobs at hand.
While this standalone mode is certainly a nice service as it is, postfix is a full-fledged mail server, capable of receiving, forwarding, relaying, filtering of e-mails, it basically have every feature we need for a mail server.
In this tutorial you will learn:
- How to install postfix on RHEL 8 / CentOS 8
- How to verify the working service with standalone functionality.