Why doesn't GFI MailEssentials try to clean a virus from an infected attachment, but quarantines or deletes the whole attachment instead?

Answer

Most of the viruses that have been released recently did not attach themselves to other attachments but replaced the whole attachment. Therefore the whole attachment is the virus, and there would be nothing to clean. Because of this, and to gain further in performance, GFI MailEssentials just quarantine or delete the whole infected attachment.