---
name: "smap"
section: "8"
platform: "linux"
package: "fwtk"
version: "1.3-1"
release: "Debian 1.3 (Bo)"
platforms: ["linux"]
url: "https://new.carta.tech/smap/8"
---

# smap(8)

sendmail wrapper client

## NAME

smap - sendmail wrapper client

## SYNOPSIS

**smap** \[invoked from inetd\]

## DESCRIPTION

The **smap** client implements a minimal version of SMTP, accepting messages from over the network, and writing them to disk for future delivery by **smapd.** **smap** is designed to run under [chroot(2)](/chroot/2.md) as a non-privileged process, to overcome potential security risks presented by privileged mailers running where they can be accessed from over a network.

**smap** is invoked from **[inetd(8)](/inetd/8.md)** and exits when its session is completed. Each session's mail is recorded in an temporary file in its spool directory, with the SMTP envelope encoded in the heading of the file. In order to coordinate processing with **smapd** the file is locked while it is being written. As a secondary means of signalling when a message is completely gathered, the mode of the file, which is initially 644, is changed to 755. In this manner the system can identify truncated or partial files left after a system crash or reboot.

## OPTIONS

**smap** takes no command line options. All configuration rules in **netperm-table** for application "smap" are read, and the following clauses and parameters are recognized:

- **userid name**

  specify the userid that **smap** should run under. The name can be either a name from the password database, or a numeric user-ID. This userid should be the same as that under which **smapd** runs, and should have write permission to the spool directory.

- **directory pathname**

  specifies the spool directory where **smap** should store incoming messages. A [chroot(2)](/chroot/2.md) system call is used to irrevocably make the specified directory the root filesystem for the remainder of the process.

- **maxbytes value**

  specifies the maximum size of messages to gather, in bytes. If no value is set, message sizes are limited by the amount of disk space in the spool area.

- **maxrecip value**

  specifies the maximum number of recipients allowed for any message. This option is only for administrators who are worried about the more esoteric denial of service attacks.

- **timeout value**

  specifies a timeout, after which **smap** should exit if it has not collected a message. If no timeout value is specified, **smap** will never time out a connection.

## INSTALLATION

To install **smap** identify the spool directory where mail will be collected. Identify the userid that **smap** will run with, and make sure that it own the spool directory. Install smap in **/etc/inetd.conf** as follows (pathnames may change):

```
smtp stream tcp  nowait root  /usr/local/etc/smap  smap
```

After modifying **/etc/inetd.conf** it is necessary to signal inetd to reload its configuration information, and to make sure that **[sendmail(8)](/sendmail/8.md)** is no longer running on the system.

In the spool directory, it may be necessary to make an /etc directory with system-specific configuration files, if the C support library on the host UNIX requires them. Generally it is recommended to build **smap** so it is completely standalone, i.e.: a statically linked executable, linked against a resolver library that will not crash if it is unable to read /etc/resolv.conf. Alternately, a small number of support files (/etc/hosts, /etc/resolv.conf) may be required. Be careful not to install any device files, or executables in the spool directory. Test installation by using telnet to connect to the SMTP port.

**smap** assumes that **smapd** will also be running on the system. See **[smapd(8)](/smapd/8.md).**

## FILES

- **spool directory**

  ## SEE ALSO

[**netperm-table**(5)](/netperm-table/5.md) [**smapd**(8)](/smapd/8.md)

## BUGS

The support for SPECIALDOMAIN is an ugly hack.