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

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 https://emailrelay.sourceforge.net/reference.html for command line reference
        option extra_cmdline '--some-other --cmdline-options'

By default mails are stored into /var/spool/emailrelay. You may want 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 /srv/spool/'. Alternatively you can make the /var/spool/emailrelay a symlink to the disk.

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-SMTP'                
        option target 'ACCEPT'                  
        option src 'wan'                        
        option proto 'tcp'                      
        option dest_port '25'                   
        option enabled '1'                      
                                                
config rule                                     
        option name 'Allow-POP'                 
        option target 'ACCEPT'                  
        option src 'wan'                        
        option proto 'tcp'                      
        option dest_port '110'                  
        option enabled '1'  
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  • Last modified: 2022/05/15 14:13
  • by stokito