.\" $OpenBSD: smtpd.conf.5,v 1.66 2012/09/17 18:44:57 gilles Exp $ .\" .\" Copyright (c) 2008 Janne Johansson .\" Copyright (c) 2009 Jacek Masiulaniec .\" .\" Permission to use, copy, modify, and distribute this software for any .\" purpose with or without fee is hereby granted, provided that the above .\" copyright notice and this permission notice appear in all copies. .\" .\" THE SOFTWARE IS PROVIDED "AS IS" AND THE AUTHOR DISCLAIMS ALL WARRANTIES .\" WITH REGARD TO THIS SOFTWARE INCLUDING ALL IMPLIED WARRANTIES OF .\" MERCHANTABILITY AND FITNESS. IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR .\" ANY SPECIAL, DIRECT, INDIRECT, OR CONSEQUENTIAL DAMAGES OR ANY DAMAGES .\" WHATSOEVER RESULTING FROM LOSS OF USE, DATA OR PROFITS, WHETHER IN AN .\" ACTION OF CONTRACT, NEGLIGENCE OR OTHER TORTIOUS ACTION, ARISING OUT OF .\" OR IN CONNECTION WITH THE USE OR PERFORMANCE OF THIS SOFTWARE. .\" .\" .Dd $Mdocdate: September 17 2012 $ .Dt SMTPD.CONF 5 .Os .Sh NAME .Nm smtpd.conf .Nd Simple Mail Transfer Protocol daemon configuration file .Sh DESCRIPTION .Nm is the configuration file for the mail daemon .Xr smtpd 8 . .Pp The current line can be extended over multiple lines using a backslash .Pq Sq \e . Comments can be put anywhere in the file using a hash mark .Pq Sq # , and extend to the end of the current line. Care should be taken when commenting out multi-line text: the comment is effective until the end of the entire block. .Pp Argument names not beginning with a letter, digit, or underscore must be quoted. Arguments containing whitespace should be surrounded by double quotes .Pq \&" . .Pp Macros can be defined that will later be expanded in context. Macro names must start with a letter, digit, or underscore, and may contain any of those characters. Macro names may not be reserved words (for example .Ar listen , .Ar accept , .Ar port ) . Macros are not expanded inside quotes. .Pp For example: .Bd -literal -offset indent wan_if = "fxp0" listen on $wan_if listen on $wan_if tls enable auth .Ed .Pp Some configuration directives expect expansion of their parameters at runtime. Such directives (for example .Ar deliver to maildir , .Ar deliver to mda , .Ar relay via ) may use format specifiers which will be expanded before delivery or relaying. The following formats are currently supported: %a expands to the user part of the email address prior to the resolution of aliases; %u expands to the user part after aliases resolution and will typically be the system account; %d expands to the domain part of the email address; %A expands to the user part of the sender email address; %D expands to the domain part of the sender email address. .Pp Additional configuration files can be included with the .Ic include keyword, for example: .Bd -literal -offset indent include "/etc/mail/smtpd.conf.local" .Ed .Pp The syntax of .Nm is described below. .Bl -tag -width Ds .It Ic expire Ar n {s|m|h|d} Specify how long a message can stay in the queue. The default value is 4 days. For example: .Bd -literal -offset indent expire 4d # expire after 4 days expire 10h # expire after 10 hours .Ed .It Ic hostname Ar name Specify the fully qualified domain name (FQDN) of the server. By default the current host name is used, as returned by .Xr hostname 1 . .It Xo .Ic listen on Ar interface .Op Ic port Ar port .Op Ic tls | smtps .Op Ic certificate Ar name .Op Ic enable auth .Xc Specify an .Ar interface and .Ar port to listen on. An interface group, an IP address or a domain name may be used in place of .Ar interface . .Pp Secured connections are provided either using STARTTLS .Pq Ic tls , by default on port 25, or SMTPS .Pq Ic smtps , by default on port 465. Host certificates may be used for these connections, and are searched for in the .Pa /etc/mail/certs directory. If .Ic certificate is specified, a certificate .Ao Ar name Ac Ns .crt , a key .Ao Ar name Ac Ns .key , a certificate authority .Ao Ar name Ac Ns .ca and Diffie-Hellman parameters .Ao Ar name Ac Ns .dh are searched for. If no .Ic certificate is specified, the default interface name is instead used, for example .Pa fxp0.crt , .Pa fxp0.key , .Pa fxp0.ca , and .Pa fxp0.dh . If no DH parameters are provided, smtpd will use built-in parameters. Creation of certificates is documented in .Xr starttls 8 . .Pp If the .Ic enable auth parameter is used, any remote sender that passed SMTPAUTH is treated as if it was the server's local user that was sending the mail. This means that filter rules using "from local" will be matched. .It Xo .Ic map Ar map .Ic source Ar type Ar source .Xc Maps are used to provide additional configuration information for .Xr smtpd 8 . .Pp .Ar map may be named freely. .Pp .Ar type may be one of the following: .Pp .Bl -tag -width "fileXXX" -compact .It db Mappings are stored in a file created using .Xr makemap 8 . This is the default type if none is specified. .It plain Mappings are stored in a plain text file using the same format as used to generate .Xr makemap 8 mappings. .El .Pp .Ar source specifies the source of the map data. It must be an absolute path to a file for the .Dq plain and .Dq db map types. .It Ic size Ar n Specify a maximum message size of .Ar n bytes. The argument may contain a multiplier, as documented in .Xr scan_scaled 3 . .It Xo .Ic queue .Ic compression Op Ar gzip .Xc Enable transparent deflating and inflating of all envelopes and messages. The only supported algorithm at the moment is gzip. Envelopes and messages may be inspected using .Xr gzcat 1 . .It Ic accept | reject .Xr smtpd 8 accepts and rejects messages based on information gathered during the SMTP session. .Pp For each message processed by the daemon, the filter rules are evaluated in sequential order, from first to last. The first matching rule decides what action is taken. If no rule matches the message, the default action is to reject the message. .Pp Following the accept/reject decision comes the client's IP address filter: .Bl -tag -width Ds .It Ic from all Make the rule match regardless of the IP of connecting client. .It Ic from local The rule matches only locally originating connections. This is the default, and may be omitted. .It Ic from Ar network The rule matches if the connection is made from the specified .Ar network , specified in CIDR notation. .El .Pp Next comes the selection based on the domain the message is sent to: .Bl -tag -width Ds .It Xo .Ic for all .Op Ic alias Ar aliases .Xc Make the rule match regardless of the domain it is sent to. If specified, .Ar aliases is used for looking up alternative destinations for all addresses. .It Xo .Ic for domain Ar domain .Op Ic alias Ar aliases .Xc This rule applies to mail destined for the specified .Ar domain . This parameter supports the .Sq * wildcard, so that a single rule for all sub-domains can be used, for example: .Bd -literal -offset indent accept for domain "*.example.com" deliver to mbox .Ed .Pp If specified, .Ar aliases is used for looking up alternative destinations for addresses in this .Ar domain . .It Xo .Ic for domain map Ar domains .Op Ic alias Ar aliases .Xc This rule applies to mail destined to domains which are part of the map .Ar domains . .Pp If specified, .Ar aliases is used for looking up alternative destinations for addresses in these .Ar domains . .It Xo .Ic for local .Op Ic alias Ar map .Xc This rule applies to mail destined to .Dq localhost and to the server's fully qualified domain name, as returned by .Xr hostname 1 . .It Ic for virtual map Ar vmap This rule applies to mail destined for the virtual domains specified in the map .Ar vmap . For an example of how to configure a virtual map, see .Xr makemap 8 . .El .Pp Finally, the method of delivery is specified: .Bl -tag -width Ds .It Ic deliver to maildir Ar path Mail is added to a maildir. Its location, .Ar path , may contain format specifiers that are expanded before use (see above). If .Ar path is not provided, then .Pa ~/Maildir is assumed. .It Ic deliver to mbox Mail is delivered to the local user's system mailbox in .Pa /var/mail . .It Ic deliver to mda Ar program Mail is piped to the specified .Ar program , which is run with the privileges of the user the message is destined to. This parameter may use conversion specifiers that are expanded before use (see above). .It Xo .Ic relay .Op Ic backup Ar mx .Op Ic as Ar address .Xc Mail is relayed. The routing decision is based on the DNS system. .Pp If the .Ic backup parameter is specified, the current server will act as a backup server for the target domain. Accepted mails are only relayed through servers with a lower preference value in the MX record for the domain than the one specified in .Ar mx . .Pp If the .Ic as parameter is specified, .Xr smtpd 8 will rewrite the sender advertised in the SMTP session. .Ar address may be a user, a domain prefixed with .Sq @ , or an email address, causing smtpd to rewrite the user-part, the domain-part, or the entire address, respectively. .It Xo .Ic relay via .Ar host .Op Ic certificate Ar name .Op Ic auth Ar map .Op Ic as Ar address .Xc Mail is relayed through the specified .Ar host expressed as a URL. For example: .Bd -literal -offset indent smtp://mx1.example.org # use SMTP smtp://mx1.example.org:4321 # use SMTP \e # with port 4321 .Ed .Pp The communication channel may be secured using one of the secure schemas. For example: .Bd -literal -offset indent tls://mx1.example.org # use TLS smtps://mx1.example.org # use SMTPS ssl://mx1.example.org # try SMTPS and \e # fallback to TLS .Ed .Pp In addition, credentials for authenticated relaying may be provided when using a secure schema. For example: .Bd -literal -offset indent tls+auth://mx1.example.org # AUTH over TLS smtps+auth://mx1.example.org # AUTH over SMTPS ssl+auth://mx1.example.org # AUTH over either \e # SMTPS or TLS .Ed .Pp If a certificate .Ar name is specified and exists in the .Pa /etc/mail/certs directory with a .crt extension, it will be used if the remote server requests a client certificate. Creation of certificates is documented in .Xr starttls 8 . .Pp If an SMTPAUTH session with .Ar host is desired, the .Ic auth parameter is used to specify the .Ar map that holds the credentials. .Pp If the .Ic as parameter is specified, .Xr smtpd 8 will rewrite the sender advertised in the SMTP session. .Ar address may be a user, a domain prefixed with .Sq @ , or an email address, causing smtpd to rewrite the user-part, the domain-part, or the entire address, respectively. .It Ic expire Ar n {s|m|h|d} Specify how long a message that matched this rule can stay in the queue. .El .El .Sh FILES .Bl -tag -width "/etc/mail/smtpd.confXXX" -compact .It Pa /etc/mail/smtpd.conf Default .Xr smtpd 8 configuration file. .It Pa /var/spool/smtpd/ Spool directories for mail during processing. .El .Sh EXAMPLES The default .Nm file which ships with .Ox listens on the loopback network interface (lo0), and allows for mail from users and daemons on the local machine, as well as permitting email to remote servers. Some more complex configurations are given below. .Pp This first example is the same as the default configuration, but all outgoing mail is forwarded to a remote SMTP server. A secrets file is needed to specify a username and password: .Bd -literal -offset indent # touch /etc/mail/secrets # chmod 640 /etc/mail/secrets # chown root:_smtpd /etc/mail/secrets # echo "smtp.example.com username:password" \*(Gt /etc/mail/secrets # makemap /etc/mail/secrets .Ed .Pp .Nm would look like this: .Bd -literal -offset indent listen on lo0 map aliases source db "/etc/mail/aliases.db" map secrets source db "/etc/mail/secrets.db" accept for local alias aliases deliver to mbox accept for all relay via tls+auth://smtp.example.com auth secrets .Ed .Pp In this second example, the aim is to permit mail relaying for any user that can authenticate using their normal login credentials. An RSA certificate must be provided to prove the server's identity. The mail server has an external interface bnx0. Mail with a local destination should be sent to an external mda. First, the RSA certificate is created: .Bd -literal -offset indent # openssl genrsa -out /etc/mail/certs/mail.example.com.key 4096 # openssl req -new -x509 -key /etc/mail/certs/mail.example.com.key \e -out /etc/mail/certs/mail.example.com.crt -days 365 # chmod 600 /etc/mail/certs/mail.example.com.* .Ed .Pp In the example above, a certificate valid for one year was created. The configuration file would look like this: .Bd -literal -offset indent listen on lo0 listen on bnx0 tls certificate mail.example.com enable auth map aliases source db "/etc/mail/aliases.db" accept for local deliver to mda "/path/to/mda -f -" accept from all for domain example.org \e deliver to mda "/path/to/mda -f -" accept for all relay .Ed .Sh SEE ALSO .Xr mailer.conf 5 , .Xr makemap 8 , .Xr smtpd 8 .Sh HISTORY .Xr smtpd 8 first appeared in .Ox 4.6 .