lzma mdboxes with unexpected EOF

[Bjoern Franke]

Hi,

I'm running dovecot 2.3.13 (until 05.01. it was 2.3.11.3) on Arch Linux
and used lzma compressed mdboxes. Yesterday a user called me that she is
missing all mails from the beginning of the month until now. I took a
look into the logs and saw several "lzma.read [...] unexpected EOF at
<....>". As I had no clue why the mdboxes are broken, I tried to convert
all 3 mailboxes to Maildir using "doveadm sync" to prevent further
issues and stumbled upon several lzma errors for mdbox files of my own
user. So I wrote a script which took the offset and size via "doveadm
dump" und then dds the xz parts out of the broken mdboxes and extracts
them via 7z.

But I'm wondering why that happened at all. I stumpled upon [1] but
there was no further discussion about it.

Best Regards
Bjoern

[1]https://dovecot.org/pipermail/dovecot/2019-September/117007.html