This page explains the variables found in
In most cases
mailu.env is setup correctly by the setup utility and can be left as-is.
However, some advanced settings or modifications can be done by modifying this file.
SECRET_KEY must be changed for every setup and set to a 16 bytes
randomly generated value. It is intended to secure authentication cookies
among other critical uses. This can be generated with a utility such as pwgen,
which can be installed on most Linux systems:
apt-get install pwgen pwgen 16 1
DOMAIN holds the main e-mail domain for the server. This email domain
is used for bounce emails, for generating the postmaster email and other
HOSTNAMES are all public hostnames for the mail server. Mailu supports
a mail server with multiple hostnames. The first declared hostname is the main
hostname and will be exposed over SMTP, IMAP, etc.
SUBNET defines the address range of the docker network used by Mailu.
This should not conflict with any networks to which your system is connected.
(Internal and external!). Normally this does not need to be changed,
unless there is a conflict with existing networks.
POSTMASTER is the local part of the postmaster email address. It is
recommended to setup a generic value and later configure a mail alias for that
AUTH_RATELIMIT holds a security setting for fighting attackers that
try to guess user passwords. The value is the limit of requests that a single
IP address can perform against IMAP, POP and SMTP authentication endpoints.
TLS_FLAVOR sets how Mailu handles TLS connections. Setting this value to
notls will cause Mailu not to server any web content! More on TLS certificates.
MESSAGE_SIZE_LIMIT is the maximum size of a single email. It should not
be too low to avoid dropping legitimate emails and should not be too high to
avoid filling the disks with large junk emails.
RELAYNETS are network addresses for which mail is relayed for free with
no authentication required. This should be used with great care. If you want other
Docker services’ outbound mail to be relayed, you can set this to
to include all Docker networks. The default is to leave this empty.
RELAYHOST is an optional address of a mail server relaying all outgoing
FETCHMAIL_DELAY is a delay (in seconds) for the fetchmail service to
go and fetch new email if available. Do not use too short delays if you do not
want to be blacklisted by external services, but not too long delays if you
want to receive your email in time.
RECIPIENT_DELIMITED is a character used to delimit localpart from a
custom address part. For instance, if set to
+, users can use addresses
firstname.lastname@example.org to deliver mail to
This is useful to provide external parties with different email addresses and
later classify incoming mail based on the custom part.
DMARC_RUF are DMARC protocol specific values. They hold
the localpart for DMARC rua and ruf email addresses.
WEB_ADMIN contains the path to the main admin interface, while
WEB_WEBMAIL contains the path to the Web email client.
WEBROOT_REDIRECT redirects all non-found queries to the set path.
WEBROOT_REDIRECT value disables redirecting and enables classic
behavior of a 404 result when not found.
All three options need a leading slash (
/) to work.
WEBROOT_REDIRECThas to point to a valid path on the webserver. This means it cannot point to any services which are not enabled. For example, don’t point it to
WEBSITE are customization options for the panel menu
in the admin interface, while
SITENAME is a customization option for
every Web interface.
PASSWORD_SCHEME is the password encryption scheme. You should use the
default value, unless you are importing password from a separate system and
want to keep using the old password encryption scheme.
LOG_LEVEL setting is used by the python start-up scripts as a logging threshold.
Log messages equal or higher than this priority will be printed.
Can be one of: CRITICAL, ERROR, WARNING, INFO, DEBUG or NOTSET.
See the python docs for more information.
Various environment variables
HOST_* can be used to run Mailu containers
separately from a supported orchestrator. It is used by the various components
to find the location of the other containers it depends on. They can contain an
optional port number. Those variables are:
HOST_IMAP: the container that is running the IMAP server (default:
imap, port 143)
HOST_LMTP: the container that is running the LMTP server (default:
HOST_HOSTIMAP: the container that is running the IMAP server for the webmail (default:
imap, port 10143)
HOST_POP3: the container that is running the POP3 server (default:
imap, port 110)
HOST_SMTP: the container that is running the SMTP server (default:
smtp, port 25)
HOST_AUTHSMTP: the container that is running the authenticated SMTP server for the webnmail (default:
smtp, port 10025)
HOST_ADMIN: the container that is running the admin interface (default:
HOST_ANTISPAM: the container that is running the antispam service (default:
HOST_WEBMAIL: the container that is running the webmail (default:
HOST_WEBDAV: the container that is running the webdav server (default:
HOST_REDIS: the container that is running the redis daemon (default:
Additional variables are used to locate other containers without dialing a specific port number. It is used to either whitelist connection from these addresses or connect to containers on the docker network:
FRONT_ADDRESS: the nginx container address (default:
WEBMAIL_ADDRESS: the webmail container address (default:
IMAP_ADDRESS: the webmail container address (default: