what's the utility of the BAD_CTE_7BIT check?

[fauno]

Classification (Please choose one option):

• [] Crash/Hang/Data loss
• WebUI/Usability
• Serious bug
• Other bug
• Feature
• Enhancement

Reproducibility (Please choose one option):

• Always
• Sometimes
• Rarely
• Unable
• I didn’t try
• Not applicable

Rspamd version:

1.5.3

Operation system, CPU, memory and environment:

Parabola GNU/Linux-libre

Description (Please provide a descriptive summary of the issue):

While helping loomio debug why some of their email notifications are being classified as spam by rspamd, I found multipart emails with mixed Content-Transfer-Encoding headers are given 3 points for BAD_CTE_7BIT. For instance, main CTE is set as 7bit and also the text/plain part, but the text/html is quoted-printable. I don't understand much C but I think it's because of the mixed CTE headers? If that's so, I looked for some github notifications with non-ascii characters and I found they were also given this score because of main CTE 7bit and both parts being quoted-printable. Is this a bad practice on their side? I couldn't find any recommendation otherwise (I don't know the proper RFCs)

References:

• loomio.org email marked as spam loomio/loomio#4022
• Use multipart/alternative for email encoding loomio/loomio#4023
• https://github.com/vstakhov/rspamd/blob/master/src/libmime/mime_expressions.c#L1277

Compile errors (if any):

Steps to reproduce:

Look for Content-Transfer-Encoding and X-Spamd-Result headers

Expected results:

Actual results:

Debugging information (see details here):

Configuration:

Stock configuration

Additional information:

[gdpelican]

@vstakhov Can this be considered resolved with the new commits? What was the issue to begin with?

[stale]

This issue has been automatically marked as stale because it has not had recent activity. It will be closed if no further activity occurs. Thank you for your contributions.