zurück zur Anleitung zum Mailsystem

Forward file items

The contents of the file or inline string are a list of addresses, file names, or pipe commands, separated by commas or newlines. Items that are empty are ignored. This includes items consisting solely of RFC 822 address comments. If an item is entirely enclosed in double quotes, these are removed, but otherwise double quotes are retained, because some forms of mail address require the use of double quotes, though never enclosing the whole address.

Lines starting with a # character are comments, and are ignored, and # may also appear following a comma, in which case everything between the # and the end of the line is ignored. If the file is empty, or contains only blank lines and comments, the director behaves as if it did not exist.

If a message is addressed to two or more different local parts, each of which results in an expansion that generates an identical file name or pipe command, different deliveries occur, though of course each delivery process runs with different values in the LOCAL_PART environment variable, and with different uids (in the common case). This happens only if the immediate ancestors of the pipes or files are different local parts. If several different local parts generate an intermediate alias which in turn generates a pipe or file delivery, only a single delivery is done, because the duplicate intermediate addresses are discarded.

• An address item may safely be the same local part as the one currently under consideration, because a director is automatically skipped if any ancestor has the same local part and was processed by that director. Thus a user with login name spqr who wants to preserve a copy of mail and also forward it somewhere else can set up a file such as

  spqr, spqr@st.else.where
  

  without provoking a loop. A backslash before an unqualified local part is permitted for compatibility with other mailers, but is not necessary for loop prevention. The presence or absence of a backslash does, however, make a difference when there is more than one local domain. Without a backslash, an unqualified local part is qualified with the contents of qualify_recipient unless qualify_preserve_domain is set, but if a backslash is present, the local part is always qualified with the domain of the incoming address. Care must be taken if there are alias names for local users. For example if the system alias file contains

  Sam.Reman: spqr
  
  

  then

  Sam.Reman, spqr@reme.else.where
  

  in spqr's forward file fails on an incoming message addressed to Sam.Reman, because the aliasfile director does not process Sam.Reman the second time round, having previously done so. The forward file should really contain

  spqr, spqr@reme.else.where
  
  

  but because this is such a common error, the check_ancestor option (see below) exists to provide a way to get round it.
• An item is interpreted as a file name if it begins with `/' and does not parse as a valid RFC 822 address that includes a domain. For example,

  /home/world/shadow
  

  is treated as a file name, but

  
  /s=molari/o=babylon/@x400gate.way
  
  

  is treated as an address. For a file name, a transport must be specified using the file_transport option. However, if the generated path name ends with a forward slash character, it is interpreted as a directory name rather than a file name, and directory_transport is used instead. If it ends with two slashes, directory2_transport is required. This makes it possible to support two different kinds of directory delivery simultaneously. If an item is /dev/null, delivery to it is bypassed at a high level, and the log entry shows `**bypassed**' instead of a transport name. This avoids the need for a user and group, which are necessary for a genuine delivery to a file. When the file name is not /dev/null, either the director or the transport must specify a user and group under which to run the delivery. If check_local_user is set, the uid and gid from the passwd file are used as defaults for the generic user and group options.
• An item is treated as a pipe command if it begins with `|' and does not parse as a valid RFC 822 address that includes a domain. A transport for running the command must be specified by the pipe_transport option. Either the director or the transport must specify a user and group under which to run the delivery. If check_local_user is set, the uid and gid from the passwd file are used as defaults for the generic user and group options. Both single and double quotes can be used for enclosing individual arguments to the pipe command; no interpretation of escapes is done for single quotes. If the command contains a comma character, it is necessary to put the whole item in double quotes, for example:

  "|/some/command ready,steady,go"
  

  since items are terminated by commas. Do not, however, quote just the command. An item such as

  |"/some/command ready,steady,go"
  

  is interpreted as a pipe with a rather strange command name, and no arguments.
• Instead of an address, file name, or pipe command, an item of the form

  :include:<path name>
  
  

  may appear, in which case a list of addresses is taken from the given file and included at that point, unless the forbid_include option is set. There are some security considerations when such an item is included in a user's `.forward' file:
  1. If the seteuid() function is being used to read the main file as a specific user (see seteuid below) then the included file is read as the same user.
  2. Otherwise Exim is running as root at this point. If check_local_user is set, or if an explicit directory is specified by file_directory, then any included files must be within the home or given directory, and no symbolic links are permitted below the directory name.
  3. If neither check_local_user nor file_directory is set when seteuid() is not in use, included files are not permitted.