Unable to install Plesk Email Security extension: The value of variable $myhostname should have been a fully qualified domain name

Ivan Kamnev

Updated January 13, 2026 19:06

kb: technical ext: pes Plesk Obsidian for Linux ABT: Group B

Applicable to:

Unable to install the Plesk Email Security extension with the error below:

PLESK_ERROR: Execution pleskrc has failed with exit code 1, stdout: INFO: [Sat Feb 8 16:52:46 JST 2020]: Service: amavisd, Action: restart
Trying to restart service amavisd... failed

PLESK_ERROR: Excution package has failed with exit code 1, stdout: , stderr: ERROR:main:Command '['apt-get', '-q', '--assume-yes', '-o', 'Dpkg::Options::=--force-confdef', '-o', 'Dpkg::Options::=--force-confold', '-o', 'APT::Install-Recommends=no', '--purge', 'install', 'amavisd-new']' returned non-zero exit status 100
The output of the command below shows the following error:

# journalctl -u amavisd
The value of variable $myhostname is "example", but should have been a fully qualified domain name; perhaps uname(3) did not provide such.

Amavis (the component of Plesk Email Security) requires a hostname configured as FQDN.

Log into Plesk.
Go to Tools & Settings > Server Settings.
In the Full hostname * field specify the FQDN hostname for example as shown below:
Scroll down and press the OK button to apply the changes.
Reinstall the Plesk Email Security extension.

Solution using the SSH access

Log into the server via SSH.
Execute the command below to set FQDN hostname:

# hostnamectl set-hostname example.com

Note: replace the example.com with the required FQDN hostname.
Run the commands below one by one to reinstall the Plesk Email Security extension:

# plesk bin extension -u email-security

# plesk bin extension -i email-security