MIMEINCS

Syntax
Description
Default Setting
Resource Variables
Examples
- Supporting Message-based Attachments
Version
See Also

Syntax

Envariable: N/A
Element: <MIMEINCS>
content-type
content-type
...
</MIMEINCS>
Command-line Option: N/A

Description

MIMEINCS defines the list of content-types (aka media-types) to allow. If the MIMEINCS resource is not empty, only media-types listed will be allowed. All other media-types will be excluded.

For example, if MIMEINCS is set to the following:

<MIMEIncs>
text/plain
text/html
</MIMEIncs>

Then only text/plain and text/html media-types are allowed. All other media-types will be excluded.

NOTE:

If a media-type is listed in the MIMEEXCS, it is always excluded, regardless of the value of MIMEINCS.

If all you want to do is exclude a specified set of media-types, then use the MIMEEXCS resource instead.

Base types can also be listed to allow all media-types with a give base. For example, image/jpg will only allow JPEG images, but image will allow all images.

NOTE:

Use care when setting MIMEINCS since you may unintentionally exclude media-types that you do not want to exclude. See Examples below.

Examples

MIMEINCS provides strict control over the allowed media-types in your archives, allowing for better security. For example:

<MIMEIncs>
text/plain
</MIMEIncs>

Will only allow text/plain data. All other types will be excluded. For some, this may be ideal, but for many, it may be too restrictive: disallowing other text media types that do not pose security risks. Therefore, the following may be prefered:

<MIMEIncs>
text
</MIMEIncs>

All text media-types are allowed. However, HTML (text/html) does pose security problems. Therefore, you may want to allow all text media-types, excluding HTML:

<MIMEIncs>
text
</MIMEIncs>

<MIMEExcs>
text/html
</MIMEExcs>

Supporting Message-based Attachments

The media-type message/rfc822 is commonly used when one message includes another. For example, popular MUAs provide a "forward-as-attachment" feature when reading an email message. When used, MUAs will specify the message/rfc822 media-type for the attachment.

The following is a more liberal MIMEINCS setting that allows media-types commonly used in email, allows forward-as-attachment cases, and keeps security risks to a minimum:

<MIMEIncs>
text
image
message
</MIMEIncs>

NOTE:

Attached messages will still be restricted to the media-types listed in MIMEINCS. For example, if a forwarded message includes a video attachment, the video attachment will be excluded.

Version

2.6.12