Yes, it is safe and it is supposed to be on the PC.
Files that contain the .ecf file extension are most commonly associated with the Microsoft Outlook email and calendar software application. The Microsoft Exchange Server also uses the .ecf file suffix. The ECF files that are used with the Microsoft Outlook software contain add-ins that allow users to install extra features into the Outlook application. The add-in files can be managed using the Add-In Manager that is found in the "Advanced Options feature in the Outlook program.
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