emailFilter.xml is for creating filter rules for SMTP-based alerts.
You can SSH in to the Analytics VM and vi edit emailFilter.xml... OR if your Linux skills are lacking you can use a SCP client (WinSCP, Fugu, etc), and edit the file via a pretty GUI.
File is here: /usr/lib/vmware-vcops/user/plugins/outbound/filter_alertplugin/conf/emailFilter.xml
If you want to find a file in the future, you can do this command: find / -name emailFilter.xml