I have following in my neomuttrc:

mailboxes \
$spool_file \
$record \
$trash \
=Archive \
`find ~/Documents/mail -type f | sort -r | paste -sd ' '`

~/Documents/mail contains ~20 years of mail archive as regular mbox files and since 2023-05-12 startup takes ~30 seconds.

neomutt -d5 generated 4.8G .neomuttdebug0 containing 37268323 lines starting with:
is_from() Could not parse From line: ...

git bisect says:
3cd41dd is the first bad commit.

If I remove ~/Documents/mail part then everything is blazing fast again.