ZynBit will show that the email has been filed in Salesforce if your Outlook Categories are set to display. The teal colored icon below shows emails which have been filed.
This is a quick and easy way to make sure you have filed everything you intended. Note that setting this category does not file the email in Salesforce. It is simply a visual reminder that this work has been done.
It is possible to configure the calendar to show the Filed with ZynBit category using the setting AddZynBitCategoryToAllOutlookItems. For more information on the Outlook desktop settings file, review the article Configuration Settings File And Options For Outlook Desktop
To ensure that you see this information, open the View tab and select Add Columns in the center of the page. Categories should be on the right hand side as shown here. If not, select the column from the left side, click Add and then OK.