First we have to download magicspam from there website.
Unzip it with WinRar or some other ZIP extractor.
Open meta.xml with text editor and find <plesk_min_version>17.9.0</plesk_min_version> line
Change it to <plesk_min_version>17.8.0</plesk_min_version> (or lower no different)
Upload file to your plesk server
Install it from SSH with this command: plesk bin extension –install /path/to/file.zip