Bug ID: 1840
Summary: Exim does not log a Message-ID it generates to fix up
a missing one
When a message arrives over SMTP with submission mode set and has no
"Message-ID:" header, Exim generates a message-id and adds the header line to
the message. This is documented in section 47.1 of the Exim Specification.
However the generated message-id does not get recorded anywhere in the log
files (eg, mainlog). This makes it impossible to supply the Message-ID to the
postmaster of the next-hop mail server to ease tracing a message.
The fault lies in the receive.c file within the receive_msg() function.
After reading and parsing the incoming headers Exim reaches a section of code
that checks whether the msgid_header variable is NULL and, if submission mode
is set, generates a message-id then uses header_add_at_position() to add the
line to the message.
However this code does not record the generated value in the msgid_header
Further down the function is the logging code that forms and outputs the
incoming "<=" log line. This checks msgid_header, finds it still NULL, so
having nothing to log does not add the "id messageidvalue" text to the log line
A possible solution is to modify the code that generates the value for a
missing message-id to also store the generated value in msgid_header. This
would give it a value so that when the logging code is reached it is output.
A potential drawback is that there would be no indication the value logged was
generated by the receiving Exim rather than arriving with the message itself.
This could conceivably lead to a postmaster quoting a (generated) message-id to
an upstream postmaster in an effort to help them trace a message back. Of
course as Exim generated the message-id it would not be known as that on the
However submission mode is generally expected to be used with MUAs, most of
which will generated message-ids; it is highly unlikely that a postmaster would
need to contact an upstream postmaster regarding a message for which the
receiving Exim was using submission mode and had to generate a message-id.
I'd therefore suggest the easy/straightforward solution of recording the
generated value in msgid_header so that the logging code picks it up is likely
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