The squirrelmail-20190509_0200-SVN.stable.tar.gz files are not in the correct format.
The folders below like:
squirrelmail.svn/squirrelmail/*

must be renamed to be:
squirrelmail-1.4.23-20180516_0203

then tarred up:
squirrelmail-1.4.23-20180516_0203.tar.gz