There are a number of circumstances in which addresses in messages are altered as they are handled by Exim. This can apply both to the messages’ envelopes and to their headers. The header lines that may be affected are Bcc:, Cc:, From:, Reply-To:, Sender:, and To:. Some of these changes happen automatically, whereas others are explicitly configured by the administrator.
One case of automatic rewriting is the addition of a domain to an unqualified
address, as discussed in
Chapter 13. This qualification is applied
to addresses in header lines as well as to those in envelopes. For example, if
a message is sent on a host where
qualify_domain is set to crete.example
by this command:
$ exim daedalus To: daedalus ...
the unqualified local part daedalus is transformed into the fully qualified
address firstname.lastname@example.org, both in the envelope and in the To:
header line. Messages that arrive from other hosts should not contain
unqualified addresses; you need to set
receiver_unqualified_hosts if you want to allow such messages to be
accepted (as described in
The other case in which automatic rewriting happens is when an incomplete domain is given. The routing process may cause this to be expanded into the full domain name within the current encompassing domain. For example, a header such as:
might be rewritten as:
if encountered on a host within the ...