Under File extensions you can list the file extensions to which you would like to apply the respective filter. You can, for instance, combine all executable files (such as EXE and COM files) in a single filter, while also filtering out other formats (for instance MPEG, AVI, MP3, JPEG, JPG, GIF etc.) that are a burden for your mail server due to their size. You can, of course, also filter out archive files of your choice, such as ZIP, RAR or CAB files. Please use a semicolon to separate all file extensions of a filter group.
The function Also filter attachments in embedded mails ensures that the filtering performed under File extensions for the selected attachment types also applies to email messages that are themselves being forwarded as email attachments. This option should generally be enabled.
Choosing Only rename attachments has the effect that attachments that are to be filtered are not deleted automatically rather just renamed. This is not only recommended for executable files (such as EXE and COM) but also for Microsoft Office files that may contain executable scripts and macros. Renaming an attachment makes it impossible to open it simply by clicking it. Instead, the user must first save (and possibly rename) the attachment before it can be used. If the checkmark for the Only rename attachments function has not been set, the respective attachments are deleted directly.
Under Suffix you can enter a character string that should be appended to the file extension (*.exe_danger, for instance), which prevents this type of file from being executed by just clicking on it. Under Insert message in mail text you can inform the recipient of the filtered email that an attachment was deleted or renamed based on a filter rule.