mdbox + sis attachments. Error stream is larger than expected by 1 byte

[Oleg Krivonosov]

Hello!

I use Dovecot 2.3.4.1-5+deb10u1 (Debian 10 x64) with mdbox, sis and imap.

I catch many errors with attachments "Stream is larger than expected" by 1
byte in emails from Xerox WorkCentre 3345.

Examples:
Sep 20 23:20:04 mailserver dovecot: imap(wasya)<606><AG1zywGTVodVrE84>:
Error: Mailbox INBOX: UID=5002:
read(attachments-connector(/var/mail/virtual/wasya/mdbox/storage/m.210))
failed:
read(/var/mail/attachments/b3/56/b3563977baf186928d38f81480b6443cf6d6d7e4-b86d80062ab36f5d7f190000f7ccf497[base64:18
b/l]) failed: Stream is larger than expected (882801 > 882800, eof=0)
(FETCH BODY[])
Sep 20 23:32:27 mailserver dovecot: imap(wasya)<4831><n0a39wGTZ8hVyu8l>:
Error: Mailbox INBOX: UID=654996:
read(attachments-connector(/var/mail/virtual/wasya/mdbox/storage/m.4372))
failed: read(/var/mail/virtual/wasya/mdbox/storage/m.4372 trailer) failed:
Stream is larger than expected (38 > 37, eof=0) (FETCH BODY[]).

This error breaks getting email in MS Outlook and breaks viewing attachment
in the problem email.

Please help me to debug and to fix this issue.

-- 
Best regards
Oleg
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