Exim 4.10 Specification chapter 27

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# 27. The lmtp transport

The lmtp transport runs the LMTP protocol (RFC 2033) over a pipe to a specified command. It is something of a cross between the pipe and smtp transports. Exim also has support for using LMTP over TCP/IP; this is implemented as an option for the smtp transport. Because LMTP is expected to be of minority interest, the default build-time configure in src/EDITME has it commented out. You need to ensure that

      TRANSPORT_LMTP=yes

is present in your Local/Makefile in order to have the lmtp transport included in the Exim binary.

The private options of the lmtp transport are as follows:

### batch_id

Type: string, expanded
Default: unset

See the description of local delivery batching in chapter 24.

### batch_max

Type: integer
Default: 1

This limits the number of addresses that can be handled in a single delivery. Most LMTP servers can handle several addresses at once, so it is normally a good idea to increase this value. See the description of local delivery batching in chapter 24.

### command

Type: string, expanded
Default: unset

This is a mandatory option, which must be set. The string is a command which is run in a separate process. It is split up into a command name and list of arguments, each of which is separately expanded (so expansion cannot change the number of arguments). The command is run directly, not via a shell. The message is passed to the new process using the standard input and output to operate the LMTP protocol.

### timeout

Type: time
Default: 5m

The transport is aborted if the created process does not respond to LMTP commands or message input within this timeout.

Here is an example of a typical LMTP transport:

      lmtp:
        driver = lmtp
        command = /some/local/lmtp/delivery/program
        batch_max = 20
        user = exim

This delivers up to 20 addresses at a time, in a mixture of domains if necessary, running as the user exim.

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