TABLE(5) File Formats Manual TABLE(5)

tableformat description for smtpd tables

This manual page documents the file format for the various tables used in the smtpd(8) mail daemon.

The format described here applies to tables as defined in smtpd.conf(5).

There are two types of tables: lists and mappings. A list consists of a series of values, while a mapping consists of a series of keys and their associated values. The following illustrates how to declare them as static tables:

table mylist { value1, value2, value3 }
table mymapping { key1 = value1, key2 = value2, key3 = value3 }

When using a ‘file’ table, a list will be written with each value on a line by itself.


A mapping will be written with each key and value on a line, whitespace and an optional colon separating both columns:

key1:	value1
key2	value2
key3	value3

Blank lines, leading and trailing spaces and tabs are ignored. Lines whose first non-space character is a hash mark (‘#’) are comments and are ignored. To force the parsing of a file table as a list rather than a mapping, use this special comment:

# @list

A file table can be converted to a Berkeley database using the makemap(8) utility with no syntax change.

Tables using a ‘file’ or Berkeley DB backend will be referenced as follows:

table name file:/path/to/file
table name db:/path/to/file.db

Aliasing tables are mappings that associate a recipient to one or many destinations. They can be used in two contexts: primary domain aliases and virtual domain mapping.

action name method alias <table>
action name method virtual <table>

In a primary domain context, the key is the user part of the recipient address, whilst the value is one or many recipients as described in aliases(5):

user1	otheruser
user2	otheruser1,otheruser2

In a virtual domain context, the key is either a user part, a full email address or a catch-all, following selection rules described in smtpd.conf(5), and the value is one or many recipients as described in aliases(5):

user1			otheruser	otheruser1,otheruser2

The following directive shares the same table format, but with a different meaning. Here, the user is allowed to send mail from the listed addresses:

listen on interface auth [...] senders <table>

Domain tables are simple lists of domains or hosts.

match for domain <table> action name
match helo <table> [...] action name

In that context, the list of domains will be matched against the recipient domain or against the HELO name advertised by the sending host, respectively. For ‘static’, ‘file’ and dbopen(3) backends, a wildcard may be used so the domain table may contain:

Credentials tables are mappings of credentials. They can be used in two contexts:

listen on interface tls [...] auth <table>
action name relay host relay-url auth <table>

In a listener context, the credentials are a mapping of username and encrypted passwords:

user1	$2b$10$hIJ4QfMcp.90nJwKqGbKM.MybArjHOTpEtoTV.DgLYAiThuoYmTSe
user2	$2b$10$bwSmUOBGcZGamIfRuXGTvuTo3VLbPG9k5yeKNMBtULBhksV5KdGsK

The passwords are to be encrypted using the smtpctl(8) encrypt subcommand.

In a relay context, the credentials are a mapping of labels and username:password pairs:

label1	user:password

The label must be unique and is used as a selector for the proper credentials when multiple credentials are valid for a single destination. The password is not encrypted as it must be provided to the remote host.

Netaddr tables are lists of IPv4 and IPv6 network addresses. They can only be used in the following context:

match from src <table> action name

When used as a "from source", the address of a client is compared to the list of addresses in the table until a match is found.

A netaddr table can contain exact addresses or netmasks, and looks as follow:

Userinfo tables are used in rule context to specify an alternate userbase, mapping virtual users to local system users by UID, GID and home directory.

action name method userbase <table>

A userinfo table looks as follows:

joe	1000:100:/home/virtual/joe
jack	1000:100:/home/virtual/jack

In this example, both joe and jack are virtual users mapped to the local system user with UID 1000 and GID 100, but different home directories. These directories may contain a forward(5) file. This can be used in conjunction with an alias table that maps an email address or the domain part to the desired virtual username. For example:     joe    jack

Source tables are lists of IPv4 and IPv6 addresses. They can only be used in the following context:

action name relay src <table>

Successive queries to the source table will return the elements one by one.

A source table looks as follow:

Mailaddr tables are lists of email addresses. They can be used in the following contexts:

match mail-from <table> action name
match rcpt-to <table> action name

A mailaddr entry is used to match an email address against a username, a domain or a full email address. A "*" wildcard may be used in part of the domain name.

A mailaddr table looks as follow:


Addrname tables are used to map IP addresses to hostnames. They can be used in both listen context and relay context:

listen on interface hostnames <table>
action name relay helo-src <table>

In listen context, the table is used to look up the server name to advertise depending on the local address of the socket on which a connection is accepted. In relay context, the table is used to determine the hostname for the HELO sequence of the SMTP protocol, depending on the local address used for the outgoing connection.

The format is a mapping from inet4 or inet6 addresses to hostnames:

::1		localhost	localhost

smtpd.conf(5), makemap(8), smtpd(8)

December 27, 2023 Linux 6.8.2-arch2-1