No crashes here after insertion via drag/drop => send and reply with quoted HTML including your GIF on Win7 which most probably means that the release candidate of PM 4.8 with its new HTS/TER modules (and maybe some of my RTF tweaks involved) does a better job than the version you're currently using. If it still crashes for you after the update I might need the original message from you (zipped CNM file if possible).
I confirm that in v4.73 I don't experience the crash when inserting the animated gif via drag/drop. But when using the ordinary "Insert Image" (Bild einfügen) dialog by using the icon:
Pmail still crashs. Please test it again Michael.