to filter out email headers, don't remove footers
When creating an analytics index in Relativity, keep in mind that the option for the email header filter will only be enabled, when the setting to 'Remove english signatures and footers' to set to 'No'. If you want to remove the email header info, you'll have to also select the option to remove email signatures to 'No'. You can choose to both keep signatures and footers, and have the email header filter either set to 'Yes' or 'No'.
The email header filter will remove the to, from, date, and reply indicator fields, but not the subject line.