clam.exe is an extremely small (544 bytes!) MZ+PE executable that prints

 a nice message :-) You can use it to test attachment scanning in your ClamAV
 based mail scanner.

 
 Due to license issues libclamav does not support RAR 3.0 archives (only 2.0
 are supported). Currently only clamscan is able to scan the clam-error.rar
 file (clamd only depends on libclamav's decompressors). Please use the --unrar
 option and it will automatically switch to the external unrar utility after
 libclamav's error.