I'm not sure if it's upstreamed yet, but at least the Red Hat fork includes a patch to use unlocked libc IO which more than doubles the mbox parser performance: https://github.com/karelzak/mutt-kz/commit/0672404fc710b4af5...
Mutt's parser is woeful, it's a decade or so of hacks, and in some cases it can't even round-trip its own mboxes without corruption
I'm not sure if it's upstreamed yet, but at least the Red Hat fork includes a patch to use unlocked libc IO which more than doubles the mbox parser performance: https://github.com/karelzak/mutt-kz/commit/0672404fc710b4af5...
Mutt's parser is woeful, it's a decade or so of hacks, and in some cases it can't even round-trip its own mboxes without corruption