A esmtp configuration file consists of several options. The options
format is:
keyword=value
The equal sign is optional and can be replaced by whitespace. The value
may be enclosed in simple or double quotes, in which case special characters
can be escaped as in normal C strings.
Comments are delimited by the '#' character upto the newline character.
OPTIONS
hostname
Set SMTP host and service (port).
The format is:
host.example.org[:service]
With no whitespace surrounding the colon if service is specified.
service
may be a name from /etc/services or a decimal port number. If not specified
the port defaults to 587.
Note (from libESMTP documentation): the default port number is set to
587 since this is the port that should be used for mail submission, see RFC
2476. By choosing this default now, the API does not change behavior
unexpectedly in the future as use of the new standard becomes commonplace.
The hostport notation simplifies things for the application, the user can
type "localhost:smtp" or "localhost:25" where the application
expects a host name.
username
Set the username for authentication with the SMTP server.
Do NOT set the username and password on the system configuration file unless
you are the only user of this machine. Esmtp is not run with suid
privileges therefore the system configuration file must be readable by
everyone. If your SMTP server reuquires authentication and you are not the
only user then specify your personal SMTP account details in the user
configuration file.
password
Set the password for authentication with the SMTP server.
starttls
Whether to use the StartTLS extension.
It can be one of enabled, disabled or required. It defaults to
disabled.
certificate_passphrase
Set the certificate passphrase for the StartTLS extension.
preconnect
Shell command to execute prior to opening an SMTP connection.
This may be useful in conjunction with application-level transports (e.g.
ssh with its port-forwarding functionality) to secure the SMTP
connection. Esmtp will wait for the command to exit before
proceeding. If the command returns a non-zero status, delivery will be
aborted.
identity
Define an identity.
An identity is a set of options associated with a given address. For example:
Identities are be selected by the address specified in the -f flag. You
can have as many you like.
The options in the global section (up to the first identity option)
constitute the default identity. If no options in the global section are given
then the first defined identity is taken as the default one.
Note that the default identity settings are not shared by the other identities.
Everything (username, password, etc.) must be specified for every identity even
if they don't differ from the default identity.
mda
Set the Mail Delivery Agent (MDA).
The local delivery addresses will be inserted into the MDA command wherever you
place a %T. The mail message's From address will be inserted where you
place an %F.
Some common MDAs are "/usr/bin/procmail -d %T",
"/usr/bin/deliver" and "/usr/lib/mail.local %T".