User guide

Chapter 9: Configuring Proxied Services
114 WatchGuard Firebox System
Blocking email content types
MIME stands for Multipurpose Internet Mail Extensions, a specification
about how to pass audio, video, and graphics content by way of email or
HTML. The MIME format attaches a header to content. The header
describes the type of multimedia content contained within an email or on
a Web site. For instance, a MIME type of "application/zip" in an email
message indicates that the email contains a Zip file attachment. By
reading the MIME headers contained in an incoming email message, the
Firebox can strip certain MIME types and admit only the types you want.
You define which types of attachments are admitted and which are
denied by using the Firebox’s HTTP and SMTP proxies.
From the Incoming SMTP Proxy Properties dialog box:
1 Click the Content Types tab. Specify whether you want to block
certain file-name patterns in email attachments by enabling the
checkbox marked Allow only safe content types and block file
patterns.
2 If you want to specify file patterns to block, click the upper Add
button in the dialog box.
The Select MIME Type dialog box appears as shown in the following figure.
3 Select a MIME type. Click OK.
4 To create a new MIME type, click New Type. Enter the MIME type
and description. Click OK.
The new type appears at the bottom of the Content Types drop list. Repeat this
process for each content type. For a list of MIME content types, see the
Reference
Guide
.
The syntax used on the Content Types tab is as follows: