In Microsoft Exchange one can create Anti Malware Policies. Anti Malware Policies are policies which prevent Malware from entering your organization. Malware are attachmentso in your email which may cause harm to your computer.
One of the policies which could be set is in case a Malware is detected on the email , all the attachments are deleted. Now there is an order in which Anti Malware Policies are executed on Microsoft Exchange. The Anti Malware Policies which were created the earliest are executed first and the ones created more recently are executed the last.