You can set up a maximum Email size for any inbound communications; so Emails that exceced the maximum size are automatically rejected from the helpdesk.

As well as dictate the maximum attachment file size for Emails sent into the helpdesk from Users and Agents; you can specify what type of files are allowed and disallowed.

You can also decide if hotlinked images in incoming Emails will be downloaded by default and what the maximum size for this would be.