E-MailRelay

E-MailRelay is an e-mail store-and-forward message transfer agent and proxy server. E-MailRelay does three things: it stores any incoming e-mail messages that it receives, it forwards e-mail messages on to another remote e-mail server, and it serves up stored e-mail messages to local e-mail reader programs. More technically, it acts as a SMTP storage daemon, a SMTP forwarding agent, and a POP3 server.

E-MailRelay does not do routing of individual messages; it is not a routing MTA. It forwards all e-mail messages to a pre-configured SMTP server, regardless of any message addressing or DNS redirects.

Package emailrelay takes up to 1.4mb space and installs following files:

/usr/bin/emailrelay
/usr/bin/emailrelay-filter-copy
/usr/bin/emailrelay-passwd
/usr/bin/emailrelay-submit
/etc/config/emailrelay
/etc/emailrelay.auth

Its uci configuration is located in /etc/config/emailrelay. The config starts emailrelay command with options that are described in manual. You can also use plain config file /etc/emailrelay.conf. See https://sourceforge.net/p/emailrelay/code/HEAD/tree/trunk/etc/emailrelay.conf.template

The default emailrelay config file contains server, proxy and cmdline sections.

The possible options are listed in the table below.

Name	Type	Required	Default	Description
`enabled`	integer	yes	0	Listen SMTP
`mode`	string	yes	server, proxy or cmdline	Mode: --as-server or --as-proxy. The cmdline means append extra_cmdline
`smarthost`	string	yes	(none)	For proxy mode specify the SMTP to forward emails. The option for --as-proxy <host:port>
`port`	integer	yes	25	Port to listen incoming emails.
`remote_clients`	integer	yes	0	To allow connections from anywhere. By default only local allowed. Check your firewall to avoid spam. See --remote-clients
`address_verifier`	string	no	(none)	Runs the specified external program to verify a message recipient's e-mail address. See --address-verifier
`domain`	string	no	(none)	Specifies the network name that is used in SMTP EHLO. The default is derived from a DNS lookup of the local hostname. See --domain
`anonymous`	integer	no	0	Disables the server's SMTP VRFY command. See --anonymous
`server_tls`	integer	no	0	For server and proxy mode. See --server-tls Doesn't work in v2.1, see fix
`server_auth`	string	no	(none)	For server and proxy mode. See --server-auth and /etc/emailrelay.auth
`client_tls`	integer	no	0	For proxy mode. See --client-tls
`client_auth`	string	no	(none)	For proxy mode. See --client-auth and /etc/emailrelay.auth
`extra_cmdline`	string	no	(none)	Extra command line options. See http://emailrelay.sourceforge.net/#reference_md_Reference for command line reference

A minimal server declaration:

config emailrelay 'server'
        option enabled '0'
        option mode 'server'
        option port '25'
        option remote_clients '0'

A minimal proxy declaration:

config emailrelay 'proxy'
        option enabled '0'
        option mode 'proxy'
        option smarthost '192.0.2.1:25'
        option port '25'
        option remote_clients '0'

A minimal cmdline declaration:

config emailrelay 'cmdline'
        option enabled '0'
        option mode 'cmdline'
        # specify all arguments that should be passed to emailrelay here
        # see http://emailrelay.sourceforge.net/#reference_md_Reference for command line reference
        option extra_cmdline '--some-other --cmdline-options'

Obtain a TLS cert Then configure server_tls option and put private key and then after a comma a fullchain.

By default mails are stored into /var/spool/emailrelay. On the OpenWrt the entire /var/ directory is tmpfs stored in RAM memory and will be lost on a router reboot. So you need to change it to store them into some USB disk. To do this you have to create a folder e.g. /mnt/usb_disk/spool/ and configure emailrelay to use it by setting:

option extra_cmdline '--spool-dir /mnt/usb_disk/spool/'

In next versions of the emailrelay package you'll have a separate UCI option spool_dir

Also if you are using the “POP by name” option then you need to create a subfolders for each account

If you are using email client (MUA) like Thunderbird, Outlook then you can fetch received mails by enabling POP protocol.

option extra_cmdline '--pop --pop-auth=/etc/pop.auth'. Also you must allow an access so set option remote_clients='1'. Then you must create the /etc/pop.auth file as described in http://emailrelay.sourceforge.net/index.html#userguide_md_Running_as_a_POP_server. Please note that if you are going to read emails from internet then you have to configure TLS for security. See below how to open a port for internet.

This is a very bad idea for security and don't do this unless you know what are you doing. Add to /etc/config/firewall:

config rule
        option name 'Allow-WAN-SMTP'
        option target 'ACCEPT'
        option src 'wan'
        option proto 'tcp'
        option dest_port '25'
config rule
        option name 'Allow-WAN-SMTP-Submission'
        option target 'ACCEPT'
        option src 'wan'
        option proto 'tcp'
        option dest_port '587'  
config rule
        option name 'Allow-WAN-POP'
        option target 'ACCEPT'
        option src 'wan'
        option proto 'tcp'
        option dest_port '110'

You can add these rules with command line:

uci add firewall rule
uci set firewall.wan_https_turris_rule=rule
uci set firewall.wan_https_turris_rule.name='Allow-WAN-SMTP'
uci set firewall.wan_https_turris_rule.src='wan'
uci set firewall.wan_https_turris_rule.proto='tcp'
uci set firewall.wan_https_turris_rule.dest_port='25'
uci set firewall.wan_https_turris_rule.target='ACCEPT'

uci add firewall rule
uci set firewall.wan_https_turris_rule=rule
uci set firewall.wan_https_turris_rule.name='Allow-WAN-SMTP-Submission'
uci set firewall.wan_https_turris_rule.src='wan'
uci set firewall.wan_https_turris_rule.proto='tcp'
uci set firewall.wan_https_turris_rule.dest_port='587'
uci set firewall.wan_https_turris_rule.target='ACCEPT'


uci add firewall rule
uci set firewall.wan_https_turris_rule=rule
uci set firewall.wan_https_turris_rule.name='Allow-WAN-POP'
uci set firewall.wan_https_turris_rule.src='wan'
uci set firewall.wan_https_turris_rule.proto='tcp'
uci set firewall.wan_https_turris_rule.dest_port='110'
uci set firewall.wan_https_turris_rule.target='ACCEPT'

uci commit firewall
service firewall restart

E-MailRelay

Sections

Server

Proxy

Plain commands

Useful options

Configure TLS

Mail storage location

Reading email with POP

Open ports for internet in Firewall