Hello, I am using the latest stable version of Thunderbird on Windows to read FTN (Fidonet) echo conferences that are relayed via NNTP (specifically, through Eternal September). While the message bodies are usually readable, I have persistent issues with: Unreadable or corrupted Subject headers Author names displayed with wrong characters or encoding artifacts Some headers showing as raw MIME encoding (e.g., =?KOI8-R?B?...) or complete gibberish I suspect the issue is related to legacy Cyrillic encodings such as KOI8-R or CP866, which are still common in FTN systems. It seems Thunderbird does not properly decode these in NNTP headers. I’ve attached a screenshot illustrating the problem. My questions: Is there any way to force Thunderbird to decode NNTP headers using a specific charset (like KOI8-R)? Are there any config settings, hidden preferences (about:config), or recommended add-ons to fix this behavior? Is there an open bug or known limitation related to non-UTF8 header decoding in NNTP messages? I do not face this issue when reading standard UTF-8 NNTP groups or emails — only FTN-derived groups. Thank you in advance for any advice. I’m happy to help with diagnostics or testing. Best regards, Vladislav