exim4 is an MTA. The current plan is to use exim4-daemon-light as the MTA on all the Configured Workstations.

Here's dkg installing exim4 on metis (note that once the Mail Server is set up, the CWs should be configured to send mail through that server as a "smarthost"):

[dkg@metis ~]$ sudo apt-get install exim4 mailx
Reading package lists... Done
Building dependency tree... Done
The following extra packages will be installed:
  exim4-base exim4-config exim4-daemon-light
Suggested packages:
  eximon4 exim4-doc-html exim4-doc-info
The following NEW packages will be installed:
  exim4 exim4-base exim4-config exim4-daemon-light mailx
0 upgraded, 5 newly installed, 0 to remove and 0 not upgraded.
Need to get 0B/1598kB of archives.
After unpacking 3441kB of additional disk space will be used.
Do you want to continue [Y/n]? 

Preconfiguring packages ...
Configuring Exim v4 (exim4-config)

Select the configuration type that best meets your needs.

Systems with dynamic IP addresses, including dialup systems, should generally be configured to send outgoing mail to another machine, called a "smart host" for 
delivery. You can choose to receive mail on such a system; or to have no local mail delivery, except mail for root and postmaster.

  1. internet site; mail is sent and received directly using SMTP  3. mail sent by smarthost; no local mail  5. manually convert from handcrafted Exim v3 configuration
  2. mail sent by smarthost; received via SMTP or fetchmail        4. local delivery only; not on a network  6. no configuration at this time

General type of mail configuration: 1

Selecting previously deselected package exim4-config.
(Reading database ... 60799 files and directories currently installed.)
Unpacking exim4-config (from .../exim4-config_4.52-1_all.deb) ...
Selecting previously deselected package exim4-base.
Unpacking exim4-base (from .../exim4-base_4.52-1_i386.deb) ...
Selecting previously deselected package exim4-daemon-light.
Unpacking exim4-daemon-light (from .../exim4-daemon-light_4.52-1_i386.deb) ...
Selecting previously deselected package exim4.
Unpacking exim4 (from .../archives/exim4_4.52-1_all.deb) ...
Selecting previously deselected package mailx.
Unpacking mailx (from .../mailx_1%3a8.1.2-0.20040524cvs-4ubuntu1_i386.deb) ...
Setting up exim4-config (4.52-1) ...

Setting up exim4-base (4.52-1) ...

Setting up exim4-daemon-light (4.52-1) ...
Starting MTA: exim4.

Setting up exim4 (4.52-1) ...
Setting up mailx (8.1.2-0.20040524cvs-4ubuntu1) ...

[dkg@metis ~]$