Guide: Sending Emails from the CLI

1. Basics: What do you need for email sending via CLI?

• A mail server or SMTP relay to process the emails.
• A CLI tool like mail, msmtp, or sendmail for sending emails.
• A working network configuration (DNS, internet access).

Tools we will use:

• msmtp: A simple-to-configure SMTP client.
• mailutils: For the mail command.

2. Installing the Tools

For Debian/Ubuntu:

sudo apt update
sudo apt install msmtp mailutils

For RHEL/CentOS:

sudo yum install msmtp mailx

3. Setting Up msmtp

Creating the Configuration File:

1. Create the file ~/.msmtprc:

   nano ~/.msmtprc

2. Example configuration for Gmail:

   account default
   host smtp.gmail.com
   port 587
   auth on
   user your.email@gmail.com
   password your_password
   tls on
   tls_starttls on
   logfile ~/.msmtp.log

3. Set file permissions:

   chmod 600 ~/.msmtprc

4. Setting Up Your Own Mail Server (Postfix)

A. Installing Postfix

1. Install Postfix (for Debian/Ubuntu):

   sudo apt install postfix

   For RHEL/CentOS:

   sudo yum install postfix

2. During installation, select "Internet Site" as the configuration type.

B. Configuring Postfix

Edit the main configuration file /etc/postfix/main.cf:

myhostname = your-hostname
mydomain = your-domain.com
myorigin = $mydomain
inet_interfaces = all
relayhost =

Restart Postfix after changes:

sudo systemctl restart postfix

C. Testing Postfix

Send a test email:

echo "This is a test email" | mail -s "Postfix Test" recipient@example.com

5. Sending Files via Email

Sending a Single File:

echo "Here is the attached file" | mail -s "Subject" -A /path/to/file recipient@example.com

Sending Multiple Attachments:

echo "Multiple files attached" | mail -s "Subject" -A /path/to/file1 -A /path/to/file2 recipient@example.com

6. Configuring DNS Records for Hetzner

A. Adding an SPF Record

1. Log in to the Hetzner DNS Console:

   • Go to Hetzner DNS Console.

2. Add a TXT Record for SPF:

   • Select your domain and add the following TXT record:

     @  IN  TXT  "v=spf1 mx a ip4:YOUR_IP_ADDRESS ~all"

B. Adding a DKIM Record

1. Generate a DKIM Key:

   opendkim-genkey -s default -d your-domain.com

2. Add the Public Key to Hetzner DNS:

   • Add the content of the default.txt file as a new TXT record:

     default._domainkey  IN  TXT  "v=DKIM1; k=rsa; p=PUBLIC_KEY_HERE"

C. Adding a DMARC Record

1. Add the DMARC Record:

   • Add the following TXT record to Hetzner DNS:

     _dmarc  IN  TXT  "v=DMARC1; p=none; rua=mailto:report@your-domain.com"

2. For stricter rules:

   _dmarc  IN  TXT  "v=DMARC1; p=reject; rua=mailto:report@your-domain.com"

7. Testing DNS Records

Testing SPF:

dig TXT your-domain.com

Testing DKIM:

• Send a test email to dkimvalidator.com.

Testing DMARC:

• Use tools like mxtoolbox.com.

8. Summary

• We have configured CLI email sending using msmtp and mailutils.
• A complete mail server setup with Postfix has been included.
• DNS records (SPF, DKIM, DMARC) for Hetzner were configured for secure email sending.

Good luck sending emails! 😊