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Administrator Options: Content Filtering

Content filtering can filter messages posted to your mailing list. Messages that are filtered and discarded can not be retrieved. 

All messages sent to your mailing list are subject to spam scanning on the NIU mail gateway. See ITS CanSpam support.

How content filtering works:

  • When a message is received by the list and you have enabled content filtering, the individual attachments are first compared to the filter types. If an attachment type matches an entry in the filter types, it is discarded. These are the filter_content and filter_filename_extensions* options.
  • Then, if there are pass types defined, any attachment type that does not match a pass type is also discarded. These are the pass_mime_types and pass_filename_extensions* options.
  • Attachments that are empty are removed. If the outer message is left empty after this filtering, then the whole message is discarded. Each multipart/alternative section will be replaced by just the first alternative that is non-empty after filtering.
  • Text/html parts may be converted to text/plain if the convert_html_to_plaintext option is enabled and the site is configured to allow these conversions.
Option Name Description of Options New List Default
filter_content Filter messages based on the rules setup below. No
filter_mime_types Remove messages that contain the specified MIME type. (none)
pass_mime_types Remove messages that do not contain the specified MIME type. (none)
filter_filename_extensions Filter messages that contain the specified file attachments.* (none)
pass_filename_extensions Remove message that do not contain the specified file attachments.* (none)
convert_html_to_plaintext Convert text/html parts to plain text. Yes
filter_action Action to take on a filtered item.  Forward to List Owner is strongly recommend if you choose to enable message filtering to avoid losing any messages. Any message that is discarded can not be retrieved. Discard

* Important: The NIU spam scanner scans all messages messages sent to an ITS-supported mailing list. This includes attachment blocking. These rules are enforced regardless of the individual list settings and where the destination mailbox is hosted. ITS CanSpam support .