No X Spam-Report displayed for emails opened from EML file

[runmode]

Der Button zum Anzeigen des X Spam-Reports funktioniert nicht, wenn eine E-Mail aus einer EML Datei heraus in TB geöffnet wird.

Thunderbird mail client allows to view emails from the MBOX (within a TB profile) or from an EML file. The button "Spam Scores" in Thunderbird's Message viewer (to show the single rules results of the X Spam-Report) works only if an email is opened from the list view of the account profile (MBOX). If the same email gets exportet to an EML file and opened with the TB email viewer, the button just shows a litte oval-like shaped popup. I notices that some other AddOns I have installed do work in this mode, others don't.

This behaviour can be reproduced by saving an email to an eml file and opening that file with TB.

Versions:
Windows 10
Thunderbird 91.8.1
Spam Scores 1.4.0