Hierarchy-based list featuring popular types of files grouped by their function (e.g., Executable files, Images).
File types and groups of file types for which the check boxes have been selected, are then included in the attachment filtering. The application checks attachment files for conformity with those file types.
The application determines the type of an attachment file by the file's contents, not by its extension. This allows performing a correct filtering even if the extension of an attachment file does not correspond the type of the same file (e.g., if the extensions has been changed intentionally).