due to the constant high volume of incoming spam containing attachments
which are not easy parseable for our filters, the listmasters decided
now to block the following types of attachments:
Content-Type: image/(gif|jpeg)
Content-Type: application/pdf
This is only a temporary solution, until we have better methods to
filter out spam mails containing these types of attachments.
If you know better solutions, let us know!
Maybe you should try upgrade from current SpamAssassin 2.60. 3.x should be more accurate in detecting spam. And there's sa-update and sa-compile to keep accuracy and speed good.
use those: plugins