The Eicar test virus is a component of Avira Exchange software. It is used, for example, to test the engine of the System Scanner. If the local virus scanner points out this file and reports detection, then you have to configure Real-time Protection (Guard).
Please open the configuration of the "Avira Antivirus Server" and go to PC Security → Real-Time Scanner → Exceptions. Add the following exception to "Files and folders to be ignored by the system scanner and real-time scanner".
Avira Exchange Security OEM:
C:\Program Files\Avira\Avira Exchange Security\
Avira Exchange Security SBE:
C:\Program Files\Avira\Exchange Security SBE\
Real-time Protection will not scan this directory any longer and it will not report the Eicar test virus anymore.