Block attachment .img / Bloquear extension .img

Buenos dias Quiero bloquear los emails entrantes con extension .img Me llegan mucho spam que pasa el filtro del SpamAssassin con adjuntos que tienen extension .img Como tengo que modificar el etc/cpanel_exim_system_filter ? Lo modifique de esta forma, pero sigue pasando los emails if $header_content-type: matches "(?:file)?name=(\"[^\">+\\\\.(?:ad[ep]|ba[st]|chm|cmd|com|cpl|crt|eml|exe|foo|hlp|hta|img|in[fs]|isp|jse?|lnk|md[be]|ms[cipt]|pcd|pif|reg|scr|sct|shs|url|vb[se]|ws[fhc])\")" if $header_content-type: matches "(?:file)?name=(\\\\S+\\\\.(?:ad[ep]|ba[st]|chm|cmd|com|cpl|crt|eml|exe|foo|hlp|hta|img|in[fs]|isp|jse?|lnk|md[be]|ms[cipt]|pcd|pif|reg|scr|sct|shs|url|vb[se]|ws[fhc]))" if $message_body matches "(?:Content-(?:Type:(?>\\\\s*)[\\\\w-]+/[\\\\w-]+|Disposition:(?>\\\\s*)attachment);(?>\\\\s*)(?:file)?name=|begin(?>\\\\s+)[0-7]{3,4}(?>\\\\s+))(\"[^\">+\\\\.(?:ad[ep]|ba[st]|chm|cmd|com|cpl|crt|eml|exe|foo|hlp|hta|img|in[fs]|isp|jse?|lnk|md[be]|ms[cipt]|pcd|pif|reg|scr|sct|shs|url|vb[se]|ws[fhc])\")[\\\\s;]" if $message_body matches "(?:Content-(?:Type:(?>\\\\s*)[\\\\w-]+/[\\\\w-]+|Disposition:(?>\\\\s*)attachment);(?>\\\\s*)(?:file)?name=|begin(?>\\\\s+)[0-7]{3,4}(?>\\\\s+))(\\\\S+\\\\.(?:ad[ep]|ba[st]|chm|cmd|com|cpl|crt|eml|exe|foo|hlp|hta|img|in[fs]|isp|jse?|lnk|md[be]|ms[cipt]|pcd|pif|reg|scr|sct|shs|url|vb[se]|ws[fhc]))[\\\\s;]"