GreenArrow Email Software Documentation

Installation Guide


This document describes how to install and configure GreenArrow. It’s written for experienced Linux systems administrators. Please contact GreenArrow technical support if you encounter any issues with these instructions or if you would rather have GreenArrow perform your installation.

Select a GreenArrow persistence mode

GreenArrow can store its persistent data a few different ways.

Traditional Mode

In Traditional mode, GreenArrow will store its persisted data in a variety of paths under the /var/hvmail directory structure.

Persistence Path Mode

In Persistence Path mode, GreenArrow will store its persisted data at a directory of your choosing. In this mode, GreenArrow will symlink the persisted paths under /var/hvmail to your specified path.

See this document about Persistence Path Mode for more information.

Docker Mode

GreenArrow can run under Docker. Please see this Github repository for more information on running and managing GreenArrow under Docker.

This installation guide is a good reference if you’ll be using Docker to help you understand how various parts of GreenArrow fit together, but following this guide is not required to get GreenArrow running inside of Docker.

When using Docker, individual Docker containers can be considered disposable. Your persistent data is stored on a Docker volume whose name you’ll provide during initialization and startup.


Provision a server

We recommend running GreenArrow on a dedicated server or VM. GreenArrow can co-exist with other applications, but that may introduce conflicts not addressed by this document.

The Supported Linux Distributions document lists your Linux distribution options.

For the sake of brevity, this document:

  • Refers to CentOS, Red Hat Enterprise Linux, Scientific Linux, AlmaLinux, Rocky Linux, and Amazon Linux collectively as “CentOS”.
  • Refers to Ubuntu and Debian collectively as “Debian”.

If you’re running GreenArrow with less than 4GB of RAM, it will require tuning outside the scope of this document. Please contact GreenArrow technical support if you’re in this situation.

Our Hardware Requirements document contains server sizing details.

Partitioning Guidelines

For servers dedicated to GreenArrow, we recommend the following:

  1. Create a single 20GB / partition during the Linux installation process, and leave the remaining disk space unpartitioned. We’ll discuss how to partition and format the remaining space later in this document.

    NOTE: if you or your hosting provider use RAID arrays, then please still put the disks in your desired RAID configuration, but leave the space outside of the root partition unpartitioned.

  2. If the server uses a combination of SSD and non-SSD disks, then we recommend creating the / partition on non-SSD disks, so that all available SSD disk space can be dedicated to GreenArrow.

Log in as the root user using the bash shell

Install prerequisite packages

In CentOS, we recommend selecting the “Base” package group only during the installation. If you didn’t include that package group during the installation or aren’t sure if it was included, you can install it later with:

yum -y groupinstall base

In Debian, we recommend installing the OpenSSH server and otherwise performing a minimal installation. After your operating system installation is complete, you can install the remaining prerequisites with:

apt-get -y install curl apt-transport-https gnupg

Additional repositories needed by specific distributions

AlmaLinux 8 - EPEL and PowerTools

In AlmaLinux 8 enable Powertools and EPEL repository:

dnf config-manager --set-enabled powertools
dnf install epel-release

AlmaLinux 9 and Rocky Linux 9 - EPEL and CRB

In AlmaLinux 9 and Rocky Linux 9, enable CRB (formerly PowerTools) and EPEL repositories:

dnf config-manager --set-enabled crb
dnf install epel-release

Amazon Linux 2 - EPEL

In Amazon Linux 2, enable EPEL repository:

/usr/bin/amazon-linux-extras install epel -y

Configure SELinux

GreenArrow requires that SELinux be disabled or in permissive mode.

To verify the current SELinux status and mode run:


Here’s an example sequence of commands for disabling it in most CentOS installations. Note that this will reboot your server:

sed -i 's/SELINUX=enforcing/SELINUX=disabled/' /etc/selinux/config
sed -i 's/SELINUX=permissive/SELINUX=disabled/' /etc/selinux/config

GreenArrow can run in SELinux permissive mode, but that causes additional overhead as SELinux policies are evaluated and violations logged.

If you’d like more details on this topic, then see RedHat’s SELinux documentation.

Configure time synchronization

GreenArrow works better with a stable system clock. We recommend using ntpd to keep your server’s time synchronized with NTP servers.

On RedHat-based distributions, run:

yum -y install chrony
systemctl start chronyd
systemctl enable chronyd
chronyc tracking

In Debian-based distributions, run:

apt-get -y install ntp ntpdate
service ntp stop
update-rc.d ntp defaults
service ntp start

Look for warnings on timedatectl status:

timedatectl status


               Local time: Fri 2021-10-08 12:17:23 CDT
           Universal time: Fri 2021-10-08 17:17:23 UTC
                 RTC time: Fri 2021-10-08 17:17:04
                Time zone: America/Chicago (CDT, -0500)
System clock synchronized: yes
              NTP service: active
          RTC in local TZ: yes
Warning: The system is configured to read the RTC time in the local time zone.
         This mode cannot be fully supported. It will create various problems
         with time zone changes and daylight saving time adjustments. The RTC
         time is never updated, it relies on external facilities to maintain it.
         If at all possible, use RTC in UTC by calling
         'timedatectl set-local-rtc 0'.

In this example the RTC (real-time clock) is using the local time zone. To set the RTC to use UTC run:

timedatectl set-local-rtc 0

Then check that the hardware clock and the system clock match:


Configure filesystems

We recommend that your filesystems hosting GreenArrow data (particularly the message queue) be configured in the following ways for best performance:

  • Use an XFS or Ext4 filesystem
  • Use a block size of 4096 bytes
  • Allocate one inode for every block

Here’s an example of creating an XFS filesystem that meets the above criteria. The inode recommendation is met by mkfs.xfs’s default values:

mkfs.xfs -b size=4096 -L /media/disk1 /dev/sdb1

Here’s an example of creating an Ext4 filesystem that meets the above criteria:

mkfs -t ext4 -j -b 4096 -i 4096 -L /media/disk1 /dev/sdb1

This only applies to Traditional Mode GreenArrow installations. If you’re using Persistence Path Mode, skip this step.

GreenArrow will install into /var/hvmail. If /var is not on the correct partition for installation, then you should create symlinks out to the directory where you’d like data to be stored. You can also place different parts of GreenArrow on different disks if you’d like to split the load between them. Here are the directories that are safe to put on their own disks:

Directory Contents
/var/hvmail All of GreenArrow’s data
/var/hvmail/qmail-disk/queue GreenArrow’s message queue
/var/hvmail/postgres GreenArrow’s internal PostgreSQL database
/var/hvmail/log GreenArrow’s log files and searchable databases of log data

For example, to create a symlink to relocate /var/hvmail to /media/disk1/hvmail run the following:

mkdir -p /media/disk1/hvmail
ln -s /media/disk1/hvmail /var/hvmail

This should be done before GreenArrow is installed.

Free up ports for GreenArrow

There are a number of ports that GreenArrow will bind to for network services. We recommend ensuring that these ports are free prior to installing GreenArrow.

TCP port 25 on all IP addresses – SMTP

By default, GreenArrow will want to listen on port 25 for incoming connections on all IPs. Most Linux systems ship with a default MTA of Postfix or Sendmail also listening on port 25.

We recommend you do one of the following:

  1. Disable the existing MTA

    If another MTA is already installed, it’s usually Sendmail, Exim or Postfix. The following command will check whether any of these are running:

    ps axf | grep -P 'sendmail|exim|postfix' | grep -v grep

    We recommend against uninstalling the other MTA since a subsequent package update could reinstall that MTA, and configure it to automatically start and listen on port 25. Instead, we recommend configuring the MTA not to start.

    Here’s an example of how to do this with the copy of Postfix that’s often installed by default in CentOS:

    service postfix stop && chkconfig postfix off

    Here’s an example of how to do this with an Exim installation running in Debian:

    service exim4 stop && update-rc.d exim4 disable

  2. Configure the existing MTA to listen on a port other than 25

    This will allow the existing MTA to continue to send mail, but allow GreenArrow to receive email.

  3. Configure GreenArrow to bind to a port/IP that does not conflict with the existing MTA

    It’s possible to have the existing MTA listening on port 25 on one IP and GreenArrow listen on port 25 on another IP. If you configure GreenArrow not to listen on port 25, then it will not be able to receive incoming emails, including bounces and spam complaints from the Internet. The port/IP GreenArrow binds its SMTP service to can be configured by updating the /var/hvmail/control/smtp.ipaddr and /var/hvmail/control/smtp.port files.

TCP port 587 on all IP addresses – SMTP submission

By default, GreenArrow will listen on TCP port 587 on all IP addresses.

If a service conflicts with this port, it’s usually another MTA such as Postfix.

Instruction on how to change GreenArrow’s default SMTP submission port can be found here.

TCP port 110 on all IP addresses – POP3

By default, GreenArrow will listen on TCP port 110 on all IP addresses.

Instruction on how to change GreenArrow’s default POP3 port can be found here.

TCP ports 80 and 443 on all IP addresses – HTTP and HTTPS

By default, GreenArrow will listen on TCP ports 80 and 443 on all IP addresses.

Instruction on how to change GreenArrow’s default HTTP and HTTPS ports can be found here.

We recommend being careful about changing these ports because click and open tracking links which use non-default ports can trigger spam filters.

Make firewall openings

The Firewall Configuration page describes GreenArrow’s requirements for incoming and outgoing connections.

Configure GreenArrow repository access

You will need your GreenArrow repository access key, which is a 16-character hexadecimal number. This is provided with your license.

Run these commands in CentOS, and follow the prompts:

curl > /root/setup_greenarrow_yum_repository
/bin/bash /root/setup_greenarrow_yum_repository

Run these commands in Debian, and follow the prompts:

curl > /root/setup_greenarrow_apt_repository
/bin/bash /root/setup_greenarrow_apt_repository

If you’re restoring from backups, stop here, and return to the document that you sent you here.

Install GreenArrow

The following steps install GreenArrow:

Install the packages

Now let’s install Engine and Studio. There are some shared components, so you’ll need to install both, even if you’re only using Engine.

Run these commands in CentOS:

yum -y install --enablerepo=greenarrow greenarrow && \
systemctl enable greenarrow.service

Run these commands in Debian:

apt-get update && \
apt-get -y install greenarrow && \
systemctl enable greenarrow.service && \
sed -i 's/^deb /#deb /' /etc/apt/sources.list.d/greenarrow.list

Update environment settings

GreenArrow packages make a number of changes to environment settings. To activate the changes, either log out, then back into the server, or run the following commands. If you’re logged into the server in multiple windows, then you’ll need to complete this step in each window:

. /etc/profile.d/
. /etc/profile.d/
. /etc/profile.d/
. /etc/profile.d/

If you’re performing a migration, stop here, and return to the document that you sent you here.

Initialize GreenArrow

For the next step, you’ll run the greenarrow init command. GreenArrow must be stopped (or not yet started) before running this command. This command accepts the following arguments:



If you want to run in Persistence Path Mode, add this parameter. Its argument is the path you want to use for GreenArrow’s persisted data. This path must already exist.



The email address for the new Engine and Studio administrator accounts that will be created as part of initialization.



The raw password to use for the Engine and Studio administrator accounts that will be created as part of initialization. May not be specified with --admin-password-prompt or --admin-password-hash.



Prompt for the raw password to use for the Engine and Studio administrator accounts. This helps to avoid putting your admin password into your shell history. May not be specified with --admin-password or --admin-password-hash.



An encoded password to use for the Engine and Studio administrator accounts that will be created as part of initialization. This hash is generated using the greenarrow encode_mailbox_password command. May not be specified with --admin-password or --admin-password-prompt.



Specify this argument if you want to attach a new installation of GreenArrow to an existing (already initialized) persistence path.

When using --attach:

  • The argument --persistence-path must be provided.
  • The --admin-email, --admin-password, and --admin-password-hash arguments must not be provided.


Allow GreenArrow to attach to to a previously initialized persistence path which was attached to a different version of GreenArrow. Must be used in conjunction with the --attach argument.

Persistence Path Mode

If you want to run in Persistence Path Mode, run the following to initialize GreenArrow with a new persistence path:

greenarrow init \
  --persistence-path=/Volumes/Your-GreenArrow-Path \
  --admin-email="[email protected]" \

Replace /Volumes/Your-GreenArrow-Path with the path you’ve created to use for GreenArrow’s persistent storage. The path you provide must already exist and must be an empty directory.

Replace [email protected] and password1234 above with the email address / password you’d like to use for your initial GreenArrow administrator account.

Traditional Mode

Otherwise, if you’ve elected to run in Traditional Mode, run the following to initialize GreenArrow:

greenarrow init --admin-email="[email protected]" --admin-password-prompt

Replace [email protected] above with the email address you’d like to use for your initial GreenArrow administrator account.

Your initial administrator account

Be sure to record the login information so that you can use it later.

  • If you wish to change Engine’s password or create additional Engine accounts, those procedures are documented here.
  • If you wish to change Studio’s password or create additional Studio accounts, either can be done within the ADMIN tab of Studio’s web interface.
  • Engine and Studio have some shared components, so even if you don’t have a Studio license, you’ll still have Studio installed. You just won’t be able to use Studio without a Studio license key.

Start GreenArrow

Run this command:

systemctl start greenarrow.service

Configure /etc/resolv.conf

  1. Configure the /etc/resolv.conf file to query one or more recursive DNS resolvers. For example, if you would like to query the Google and Cloudflare public DNS servers, you could populate the file with:

    echo "nameserver
    nameserver" > /etc/resolv.conf

  2. Verify that different nameservers aren’t configured elsewhere:

    1. On CentOS systems:

      find /etc/sysconfig/network-scripts/ifcfg-* /etc/sysconfig/network -type f | xargs grep 'DNS=' | grep -v 'PEERDNS='

    2. On Debian systems:

      grep dns-nameservers /etc/network/interfaces

Required GreenArrow Engine configuration

License key

Save the license key that was provided by GreenArrow to the /var/hvmail/control/license_key file.

Server name

Configure the domain name of the server. This should be a fully qualified domain name with an A record pointing to this server. The default value is the server’s hostname.

Here’s an example of how to set the name to SERVER_NAME:

hvmail_set me SERVER_NAME
hvmail_init restart

More documentation on setting the server name can be found here.

Configure HTTPS

We recommend using HTTPS for two reasons:

  1. HTTPS protects your login credentials.
  2. HTTPS is important for open tracking because some browsers and webmail clients block HTTP open tracking URLs or rewrite them to HTTPS.

We recommend using GreenArrow’s automatic TLS certificate registration, which uses Let’s Encrypt.

If you don’t want to use Let’s Encrypt, then the TLS Certificate Configuration document describes the alternatives.

Here’s how to enable automatic TLS certificate registration:

  1. Review the Let’s Encrypt subscriber agreement. Only proceed with step two if you accept the agreement.

  2. Accept the agreement by adding the following to the end of the /var/hvmail/control/greenarrow.conf file, and replacing REPLACEME with your email address. Keep the quotation marks:

    general {
      lets_encrypt_agree_to_terms_of_service yes
      lets_encrypt_registration_email "REPLACEME"

  3. Apply changes by running greenarrow_config reload.

  4. If the DNS for the server name configured above is ready, the application should be available over HTTPS in about one minute. Visit that server name over HTTPS (see the next section) to verify that it’s working. If it’s not, then the greenarrow lets_encrypt_status command can help you diagnose the problem.

If you don’t configure TLS certificates we recommend:

  1. Disable the default behavior of using HTTPS for URL Domains by adding the following to the /var/hvmail/control/greenarrow.conf file

    general {
      url_domains_always_use_tls no

Login URLs

You can connect to the web interface of GreenArrow at the server name configured above.

Engine’s web interface is accessed at the path /greenarrowadmin/ of GreenArrow’s HTTP or HTTPS server. For example, on a server named running HTTPS service on the default ports, the web interface will be accessed at:

Studio’s web interface is accessible at the path /ga/ of GreenArrow’s HTTP or HTTPS server, so using the domain as above, the login URL for GreenArrow Studio’s web interface will be:

Disable Studio services (Engine-only customers)

Studio customers should skip this step.

If you’re not using Studio, then disable its services to conserve system resources:

svc -d /service/hvmail-{studio-worker,pure-ftpd,pure-authd-studio}
touch /service/hvmail-{studio-worker,pure-ftpd,pure-authd-studio}/down

Incoming email configuration

Create at least one incoming email domain using the Server Name, along with at least one bounce mailbox, and at least one spam complaint mailbox. These will be used by GreenArrow’s bounce processor and spam complaint processor.

We recommend having at leat one incoming email domain configured (using the Server name) with root, postmaster, and abuse email accounts or email forwarders. Any additional incoming email domains can be created using these steps, or they can be configured as aliased incoming email domains if they do not need to have a unique configuration.

From address domains

Add any from address domains that you’re planning to use into GreenArrow Engine’s configuration.

IP addresses for sending

At least one IP address is required for sending.

Follow the instructions in this documentation to set up your IP addresses.

Configure SimpleMH

  1. Create a Mail Class named “default” using the Web Interface. This MailClass is used for SimpleMH mail which does not have a Mail Class defined.

  2. Either in the user interface or the configuration file, set the default URL domain.

  3. Either in the user interface or the configuration file, set the default bounce mailbox.

  4. Update the following line in the /var/hvmail/control/simplemh-config configuration file:

    1. $CAMPAIGNID_PREFIX - this is the prefix used with GreenArrow Monitor. It needs to be a unique value to your server, and needs to follow the parameters listed in the Campaign ID documentation. If you’re unsure of what to use here, you can run this to get a unique ID and paste it into the config:
      cut -c1-30 /var/hvmail/control/me

Optional GreenArrow Engine configuration

If you want the operating system to use GreenArrow for sending mail, then create the following symlinks:

ln -sf /var/hvmail/bin/sendmail /usr/sbin/sendmail
ln -sf /var/hvmail/bin/sendmail /usr/lib/sendmail

Grant SSH access to GreenArrow

GreenArrow technicians may occasionally need to SSH into your server in order to fulfill support requests. See SSH Access for details on how to grant access.

GreenArrow Monitor integration

If you have a GreenArrow Monitor account and would like to be able to view Monitor stats within Engine’s web interface, two configuration files should be created which store your Monitor account’s username and password. For example, if your username is username, and your password is password, these files would be created by running the following commands:

echo username > /var/hvmail/control/monitor.username
echo password > /var/hvmail/control/monitor.password

See the Installing and Updating your GreenArrow Monitor Seedlist document for information on how to add the GreenArrow Monitor seedlist into GreenArrow Engine or Studio.

Create URL Domain(s)

GreenArrow Engine and Studio use URL domains for click and open tracking.

We recommend creating at least one URL domain using the instructions in the URL (Click and Open Tracking) Domains page.

Tune the operating system

  1. Mount each filesystem that GreenArrow is using with the noatime option. For example, the options in /etc/fstab might look like:


    /etc/fstab updates can be applied with the mount command. For example, to apply changes to the / filesystem, run:

    mount -o remount /

  2. Disable disk quotas on each filesystem that GreenArrow is using. This is typically the default configuration on a new Linux installation.

  3. Add /var/hvmail, as well as any additional filesystem paths that GreenArrow is using to the list of paths to exclude from locate’s database by updating the PRUNEPATHS variable in the /etc/updatedb.conf file.

  4. Review your net.core.somaxconn sysctl setting (by running sysctl net.core.somaxconn).

    • This value should meet or exceed the greatest of the following calculations:
      • 4096 (This is the default as of Linux 5.4)
      • Total desired SMTP concurrency + 100
    • You can run greenarrow config recommend_sysctl to print recommended settings for your configured SMTP concurrency.
    • You can obtain your desired SMTP concurrency by summing the following:
      • The value in /var/hvmail/control/smtp.concurrency
      • The CONCURRENCY value in /var/hvmail/control/smtp2
      • The CONCURRENCY value in /var/hvmail/control/smtp3
    • greenarrow_config reload and greenarrow_config validate will warn you if your net.core.somaxconn setting is insufficient for the configured SMTP concurrency.
  5. Set vm.overcommit_memory to 1 and vm.overcommit_ratio to at least 400.

    • These settings prevent GreenArrow from being incorrectly killed by the Linux out-of-memory killer.

    • Here’s one way you can apply these settings to your system:

      cat >> /etc/sysctl.d/50-greenarrow.conf <<EOF
      vm.overcommit_memory = 1
      vm.overcommit_ratio = 400
      sysctl -p /etc/sysctl.d/50-greenarrow.conf

Tune GreenArrow Studio


The default GreenArrow PostgreSQL configuration is usually optimal in two situations:

  1. You’re running GreenArrow Engine, but not GreenArrow Studio.
  2. You have at least 4GB, but less than 6GB of RAM.

If either of the above describe your server, then you can skip the rest of this PostgreSQL tuning section. Otherwise, read on.

If your server has less than 4GB of RAM, then PostgreSQL’s default settings may be too aggressive. Please contact GreenArrow technical support if you’re in that situation.

For all other servers (servers that are running GreenArrow Studio and have at least 6GB of RAM), we recommend tuning the following PostgreSQL settings, based on the amount of RAM available to GreenArrow. If there are any non-GreenArrow applications running on your server, then you should subtract their estimated maximum memory usage from your server’s configuration before performing the calculations. For example, if your server has 8GB of RAM, and there’s a MySQL server running on it which will use a maximum of 2GB of RAM, then you should perform the calculations in this section as if the server has 6GB of total RAM.

The four settings to adjust are:

Name Recommend value
shared_buffers 25% of total RAM
effective_cache_size 50% of total RAM
work_mem 1% of total RAM
maintenance_work_mem 2% of total RAM

These values can be set by editing the /var/hvmail/control/postgres.conf file.

Here’s an example /var/hvmail/control/postgres.conf file from a server that has 8GB of RAM, and is running only GreenArrow Engine and Studio:

shared_buffers = 2GB
effective_cache_size = 4GB
work_mem = 82MB
maintenance_work_mem = 164MB

Once you’re finished editing /var/hvmail/control/postgres.conf, restart PostgreSQL to apply changes by running the following command. Please note that this will cause between 15 seconds and a few minutes of downtime, so plan accordingly if your server is currently in production:

hvmail_postgres_manager restart

Once PostgreSQL has been restarted, you can verify that it’s running by visiting GreenArrow Studio’s web interface or running the command below, which should return the string PostgreSQL is online.

echo "select ('PostgreSQL is online')" | /var/hvmail/postgres/default/bin/psql -U greenarrow

One of the more common reasons for PostgreSQL not staying up is not being able to allocate enough memory. If this happens, then add or edit the kernel.shmmax and kernel.shmall sysctl parameters. This can be set the /etc/sysctl.conf file if you’re using CentOS, or the /etc/sysctl.d/greenarrow.conf file if you’re using Debian. Make sure kernel.shmmax (specified in in bytes) exceeds PostgreSQL’s shared_buffers setting.

To apply sysctl changes, run:

sysctl -p

Final Testing

  1. Verify that some common misconfigurations are not present. Each test gets a simple pass/fail result:


  2. Verify that all services are running normally. Any services with an abnormal state will be shown in red:

    hvmail_init status

    The hvmail-qmail-smtpd3 and hvmail-dnscache services are down by default. All other services should be reported as up unless you shut them down intentionally.

  3. Send yourself a test email (replacing [email protected] with your actual email address):

    date | /var/hvmail/bin/mailsubj "GreenArrow Test Message" [email protected]

Congratulations, you’re finished installing GreenArrow! As a next step, we recommend following up with GreenArrow technical support to schedule a training call.

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