2024-07-11 Exim config for UUCP, NNCP and MSMTP
===============================================

My laptop doesn't have a static IP number. My mail service provider is
not a smart host for my laptop. That's why I've been using msmtp to
send email from the command line.

My ~/.mailrc used to contain the following:

    set sendmail="/usr/bin/msmtp"

I removed this line because I want to send mails by UUCP or NNCP,
depending on the domain used. It is only when none of these work that
I want to fall back to msmtp.

Clearly, I need to add something to my exim configuration. When
reading the exim config, it's important to understand that all the
additions come in pairs: a router and a transport.

I use Debian.

mail and ed
-----------

I use mail to read mail and ed to write mail. At least when I'm
doing this particular admin hobby project. 😂

As people will use a variety of domain names to send mail to me, I
have to decide which ones mail should recognize as being "me". That's
why ~/.mailrc contains the following:

    alternates alex@sibirocobombus,alex@campaignwiki.org,alex@campaignwiki

To read MIME-encoded mail, I use munpack -t which comes with the
mpack package.

/etc/exim4/update-exim4.conf.conf
---------------------------------

This is the file generated by sudo dpkg-reconfigure exim4-config.

Importantly, it specifies that my laptop only delivers local mail.
UUCP, NNCP and msmtp are all exceptions to that.

This config file also specifies that the exim configuration is split
into many small files. This makes it easy for me to add new files.

When I make changes, I must always run sudo update-exim4.conf.

The config files are concatenated in sort order, which is why the file
names start with numbers. All of the routers must sort before
200_exim4-config_primary because it stops all processing. It does
that because this config file says that my laptop only delivers local
mail.

    dc_eximconfig_configtype='local'
    dc_other_hostnames='melanobombus'
    dc_local_interfaces='127.0.0.1 ; ::1'
    dc_readhost='alexschroeder.ch'
    dc_relay_domains=''
    dc_minimaldns='false'
    dc_relay_nets=''
    dc_smarthost=''
    CFILEMODE='644'
    dc_use_split_config='true'
    dc_hide_mailname='false'
    dc_mailname_in_oh='true'
    dc_localdelivery='mail_spool'

/etc/exim4/conf.d/router/110_exim4-config_uucp
----------------------------------------------

The domains that get mail via UUCP are listed in /etc/exim4/uucp.

    uucp_router:
        debug_print = "R: uucp_router for $local_part@$domain"
        driver = accept
        require_files = +/usr/bin/uux
        domains = wildlsearch;/etc/exim4/uucp
        transport = rsmtp

Example /etc/exim4/uucp:

    dwalin	sibirocobombus!dwalin
    campaignwiki	sibirocobombus

That is, dwalin can only be reached via sibirocobombus and
campaignwiki is the same as sibirocobombus.

sibirocobombus is defined in /etc/uucp/sys.

Note that mail to the sibirocobombus domain itself doesn't get sent
via UUCP!

/etc/exim4/conf.d/router/111_exim4-config_nncp
----------------------------------------------

The domains that get mail via NNCP are listed in /etc/exim4/nncp.

    nncp_router:
        debug_print = "R: nncp_router for $local_part@$domain"
        driver=accept
        require_files = +/usr/bin/nncp-exec
        domains = wildlsearch;/etc/exim4/nncp
        transport = nncp

Example /etc/exim4/nncp:

    sibirocobombus          sibirocobombus
    erebor                  erebor

Compare this to the previous entry. Mail to the sibirocobombus domain
is sent via NNCP!

Both sibirocobombus and erebor must be defined in /etc/nncp.hjson.

/etc/exim4/conf.d/router/112_exim4-config_msmtp
-----------------------------------------------

This relies on the fact that the sender is a local user.

    msmtp_router:
        debug_print = "R: msmtp_router for $local_part@$domain"
        driver=accept
        user = ${lookup{$sender_address_local_part}lsearch,ret=key{/etc/passwd}}
        domains = ! +local_domains
        require_files = +/usr/bin/msmtp
        transport = msmtp

/etc/exim4/conf.d/transport/40_exim4-config_uucp
------------------------------------------------

    rsmtp:
        debug_print = "T: rsmtp for $pipe_addresses"
        driver=pipe
        command = /usr/bin/uux - -r -a${lookup{$sender_address_local_part}lsearch,ret=key{/etc/passwd}} -gC $domain_data!rsmtp
        use_bsmtp
        return_fail_output
        user=uucp
        batch_max = 100

/etc/exim4/conf.d/transport/41_exim4-config_nncp
------------------------------------------------

    nncp:
        debug_print = "T: nncp for $pipe_addresses"
        driver=pipe
        user=nncp
        command = /usr/bin/nncp-exec -noprogress -quiet $domain_data rsmtp
        use_bsmtp
        return_fail_output

/etc/exim4/conf.d/transport/42_exim4-config_msmtp
-------------------------------------------------

    msmtp:
        debug_print = "T: msmtp for $pipe_addresses"
        driver = pipe
        command = /usr/bin/msmtp --read-recipients --file=/home/${lookup{$sender_address_local_part}lsearch,ret=key{/etc/passwd}}/.config/msmtp/config
        return_fail_output

Note that this ensures that msmtp is run for each user, using their
own config files.

My config is stored in ~/.config/msmtp/config and it must necessarily
be non-interactive.

Previous blog posts:
--------------------

* 2024-06-30 Connecting the laptop to the server using UUCP

* 2024-06-29 Sending mail from the laptop to the server via NNCP

* 2024-06-28 Connecting the laptop to the server via NNCP

* 2024-06-15 Old tech: UUCP

* 2020-12-17 Rmail, about msmtp

​#Administration #Mail #UUCP #NNCP #msmtp ​#Mail #UUCP #NNCP #msmtp
​#UUCP #NNCP #msmtp ​#NNCP #msmtp ​#msmtp

2024-07-13. I think what is unfortunate in this setup is that my
sender domain is set to "alexschroeder.ch" even for mail sent via UUCP
or NNCP – which is probably not what my recipients want? Or maybe it
is. I'm actually not sure.