The SMTP-settings are required to enable sending emails via your own SMTP server directly from your eRecruiter instance, applicant portal and customer portal. The configuration of the SMTP-Server requires the following parameters:

global sender address
global sender name
SMTP host
SMTP port
SMTP user
SMTP password
SMTP over SSL
Fallback Sender

Those can be set in Administration → Miscellaneous → Mandator settings → SMTP and Email settings.
This information is to be provided by your IT department.