default-mta software package provides virtual package provided by exim4-daemon-light, you can install in your Debian 7 (Wheezy) by running the commands given below on the terminal,
$ sudo apt-get update $ sudo apt-get install default-mta
default-mta is installed in your system.
Make ensure the default-mta package were installed using the commands given below,
$ sudo dpkg-query -l | grep default-mta*
You will get with default-mta package name, version, architecture and description in a table
| Distro | Debian 7 wheezy |
| Section | Virtual packages |
| Package | default-mta |
| Version | |
| Description | virtual package provided by exim4-daemon-light |
| Sub Section | virtual |