1. Debian Exim4 User FAQ

This is work in progress, so it is probably not yet very helpful.

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1.1. Questions not categorized yet

1.1.1. When I try to deliver a message via SMTP to my Exim, I get "550 relay not permitted"

Answer not yet fleshed out.

1.1.2. I cannot connect to my Exim from my home connection. From internet hosts, it works

Answer not yet fleshed out.

1.1.3. I am trying to have exim forward mail to some internal hosts, but all I am getting is "all relevant MX records point to non-existent hosts"

A probeble cause for this might be that all MX records for the offending domain point to site local or link local IP addresses, which are ignored by the dnslookup router to protect from misconfigured external domains. The default configuration has relaxed checking for domains that the local system is configured to allow relaying to, so adding the offending domain to dc_relay_domains will most probably help.

Please note that no domain on the public Internet should have MX records pointing to site local or link local IP addresses, so you might check your externally visible MX records.

If this doesn't help, try analyzing the output of exim -d -bt some.local.part@the.offending.domain.example

[http://www.exim.org/eximwiki/FAQ/Routing_to_remote_hosts/Q0302 Upstream Exim FAQ Q0302] might help as well.

1.1.4. What do "lowest numbered MX record points to local host" or "remote host address is the local host" mean?

This is covered in [http://www.exim.org/eximwiki/FAQ/Routing_to_remote_hosts/Q0301 Upstream Exim FAQ Q0301.] The Debian default configuration has the hubbed_hosts router mentioned there already defined. Its configuration file is /etc/exim4/hubbed_hosts, and some documentation can be found in /etc/exim4/conf.d/router/150_exim4-config_hubbed_hosts.

1.1.5. What do the "DEBCONFfooDEBCONF" macros in the Debian configuration do?

When the Exim daemon is started, the dpkg-conffiles in /etc/exim4 are post-processed to the result /var/lib/exim4/config.autogenerated, which is the configuration file that Exim reads. In this post-processing step, done by update-exim4.conf, the DEBCONFfooDEBCONF strings are replaced with values pulled from /etc/exim4/update-exim4.conf.conf and system configuration.

Please note that the string DEBCONF is kind of a misnomer since the strings are _not_ directly pulled from the Debconf database, but from user-editable conffiles instead. This is a common misunderstanding.

For more information, read the update-exim4.conf man page.