Feature request - Header lines is quoted-printable encoded unnecessarily



  • Background
    Apparently quoted-printable encoding is used by spammers in hope that text will not be triggered by anti spam software or other simple MTA one liners people have written to stop incoming spam.

    Rspamd
    The anti spam software rspamd is giving each header +0.5 score if it detects a value that is unnecessarily quoted-printable encoded while all symbols are 7bit.
    rspamd headers.lua. Search for “EXCESS_QP” to see all tests.

    Feature request
    My request is to implement a programming function that only apply quoted-printable encoding if needed on values in the header. Kopano seems to encode first without checking if it’s really needed in Kopano Core 8.7.80.



  • The default score for FROM_EXCESS_QP and TO_EXCESS_QP in Rspamd is +1.2

    -- From that contains encoded characters while quoted-printable is not needed as all symbols are 7bit
    reconf['FROM_EXCESS_QP'] = {
      re = string.format('%s & !%s', from_encoded_qp, from_needs_mime),
      score = 1.2,
      description = 'From that contains encoded characters while quoted-printable is not needed as all symbols are 7bit',
      group = 'excessqp'
    }
    
    -- To that contains encoded characters while quoted-printable is not needed as all symbols are 7bit
    -- Final rule
    reconf['TO_EXCESS_QP'] = {
      re = string.format('%s & !%s', to_encoded_qp, to_needs_mime),
      score = 1.2,
      description = 'To that contains encoded characters while quoted-printable is not needed as all symbols are 7bit',
      group = 'excessqp'
    }
    

    So every mail received from a sender via Kopano gets a score +2.4 added. This is a severe problem!

    Have in mind that you can’t lower the score for FROM_EXCESS_QP in Rspamd because doing so would lower the score of mostly every real SPAM-mail.


Log in to reply