Filtering headers on a bounce

LoadFactor

• October 30, 2019 15:36

There are some circumstances where we filter messages based on content, returning a "550 User does not exist" in an attempt to get the address cleaned from spammer's send lists. Unfortunately, the bounce message usually contains the X-Spam-* headers that can tip the spammer off as to what's really going on. What I'd like to do is remove those headers from the response so the message is more convincing. Is this possible?

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  cPanelLauren

  • October 30, 2019 22:05

  Hello, First I need to point out that this is an unsupported customization and we don't recommend making this modification, but there are a couple of configuration options for this:

  • You might want to look at the remove header options from SpamAssassin here:
    • The configuration file is located here: etc/mail/spamassassin/local.cf
      
    • There's some great information on customizing SpamAssassin configuration here:
  • You could write a filter for this using headers_add and headers remove but exim only allows this is the system filter - so you'd need to customize the exim system filter.
    • There are instructions for modifying the exim system filter on cpanel servers here:
    • You can find instructions from exim on how to filter SpamAssassin headers here:

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  LoadFactor

  • October 31, 2019 02:00

  Those headers are really useful so I wouldn't want to remove them, particularly not globally. Similarly for the system filters, I wouldn't want all users to be affected. As much as I'd love to have the messages rejected at RCPT, one slip in exim and there would be hell to pay. I'm thinking the only viable option would be to pipe the message to a program, have it strip the unwanted headers and then send a bounce, pretending to be Mailer-Daemon

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