Optimizing Zimbra security and TLS settings via a script (updated May 2024)

A partner has requested a script to implement the Security tips and TLS
settings documented at https://wiki.zimbra.com/wiki/Cipher_suites and
https://wiki.zimbra.com/wiki/Secopstips . At Zimbra we love scripts!
This article shows a script that configures Zimbra with strong TLS and
security settings.


You have set up a correct hostname and DNS, to check, run the following
as user zimbra and verify zmhostname is the same as
hostname --fqdn:

zimbra@le-test:~$ source ~/bin/zmshutil; zmsetvars
zimbra@le-test:~$ zmhostname
zimbra@le-test:~$ hostname --fqdn

This script example works on a single server Zimbra installation, if you
run a multi-server set-up you need to split up the script based on your

Creating the script

Create a file /usr/local/sbin/secops-zimbra with the following


if [ $WHO != "zimbra" ]
echo "Execute this scipt as user zimbra (\"su - zimbra\")"
exit 1

source ~/bin/zmshutil; zmsetvars

echo "Setting optimal security settings"
rm -Rf /tmp/provfile

cat >> /tmp/provfile << EOF mcf zimbraPublicServiceProtocol https mcf zimbraPublicServicePort 443 mcf zimbraPublicServiceHostname $HOSTNAME mcf zimbraReverseProxySSLProtocols TLSv1.2 mcf +zimbraReverseProxySSLProtocols TLSv1.3 mcf zimbraReverseProxySSLCiphers "" mcf +zimbraResponseHeader "Strict-Transport-Security: max-age=31536000; includeSubDomains" mcf +zimbraResponseHeader "X-Content-Type-Options: nosniff" mcf +zimbraResponseHeader "X-Robots-Tag: noindex" mcf +zimbraResponseHeader "Referrer-Policy: no-referrer" mcf zimbraMailKeepOutWebCrawlers TRUE mcf zimbraSmtpSendAddMailer FALSE mcf zimbraSSLDHParam /opt/zimbra/conf/ffdhe4096.pem mcf zimbraMtaSmtpdTlsCiphers medium mcf zimbraMtaSmtpdTlsMandatoryCiphers medium mcf zimbraMtaSmtpdTlsProtocols '>=TLSv1.2'
mcf zimbraMtaTlsSecurityLevel may

ms $HOSTNAME zimbraPop3CleartextLoginEnabled FALSE
ms $HOSTNAME zimbraImapCleartextLoginEnabled FALSE

mcf zimbraLastLogonTimestampFrequency 1s
mc default zimbraPrefShortEmailAddress FALSE
mc default zimbraFeatureTwoFactorAuthAvailable TRUE
mc default zimbraFeatureTrustedDevicesEnabled FALSE

ms $HOSTNAME zimbraFileUploadMaxSize 80000000
ms $HOSTNAME zimbraMailContentMaxSize 80000000
mcf zimbraMtaMaxMessageSize 80000000
mcf zimbraFileUploadMaxSize 80000000
mcf zimbraMailContentMaxSize 80000000

sed -i 's/-server -Dhttps.protocols=TLSv1.2 -Djdk.tls.client.protocols=TLSv1.2/-server -Dhttps.protocols=TLSv1.2,TLSv1.3 -Djdk.tls.client.protocols=TLSv1.2,TLSv1.3/g' /opt/zimbra/conf/localconfig.xml
wget -q https://raw.githubusercontent.com/internetstandards/dhe_groups/master/ffdhe4096.pem -O /opt/zimbra/conf/ffdhe4096.pem

/opt/zimbra/bin/postconf -e fast_flush_domains=""
/opt/zimbra/bin/postconf -e smtpd_etrn_restrictions=reject
/opt/zimbra/bin/postconf -e disable_vrfy_command=yes
/opt/zimbra/bin/postconf -e tls_medium_cipherlist=$(/opt/zimbra/common/bin/openssl ciphers)
/opt/zimbra/bin/postconf -e tls_preempt_cipherlist=no

/opt/zimbra/bin/zmlocalconfig -e ldap_common_tlsprotocolmin="3.3"
/opt/zimbra/bin/zmlocalconfig -e ldap_common_tlsciphersuite="HIGH"
/opt/zimbra/bin/zmlocalconfig -e ldap_starttls_supported=1
/opt/zimbra/bin/zmlocalconfig -e zimbra_require_interprocess_security=1
/opt/zimbra/bin/zmlocalconfig -e ldap_starttls_required=true

/opt/zimbra/bin/zmlocalconfig -e alias_login_enabled=false
/opt/zimbra/bin/zmlocalconfig -e zimbra_same_site_cookie="Strict"

/opt/zimbra/bin/zmprov < /tmp/provfile

/opt/zimbra/bin/zmzimletctl undeploy com_zimbra_clientuploader
rm -Rf /opt/zimbra/lib/ext/com_zimbra_clientuploader

Running the script

Before running scripts make sure you have a working back-up and test
scripts in a test environment first. You can run this script as root
like this:

su - zimbra
chmod +x /usr/local/sbin/secops-zimbra

Check for changes

This script is copied from here, you can check periodically for updates:

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2 Responses to Optimizing Zimbra security and TLS settings via a script (updated May 2024)

  1. João Dias September 25, 2023 at 12:08 PM #

    After running the script, some clients (TLS 587) return the error “Invalid server key agreement parameter signature”
    Any solution?

    • Avatar photo
      Barry de Graaff September 25, 2023 at 11:43 PM #

      Please check if the client devices are up-to-date and still supported.

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