You can populate the contact directory by manually entering companies and contacts via a simple client application or by importing a list of companies/contacts - e.g. from digital visiting cards. If you have an existing company database, then it is possible to synchronise the MRX contact directory with your own database. (This depends on the database in use and would normally be done on a charged consultancy basis.)
The contact directory is published on the Internet using the LDAP protocol – which means most mail client applications will be able to view it. Of course, the client will need to be set up with the appropriate authorisation.