[Dovecot] MULTIAPPEND + literal8 issue

[Michael M Slusarz]

Background: importing a mbox file containing ~700 messages (20 MB).   
Our program splits MULTIAPPENDS into approx. 5MB chunks.  We don't use  
literal+ in order to immediately catch errors.

I can reproducibly produce the following error (2.2.2) when doing a  
MULTIAPPEND where every append is using literal8:

[...340 messages appended in 7 previous APPEND commands...]
C: 10 APPEND Test "16-Dec-2011 17:19:46 -0700" ~{3128}
[...~30 APPENDed messages...]
C:  "18-Jan-2012 12:38:21 -0700" ~{2893}
S: + OK
[...2893 octets of data...]
C:  "18-Jan-2012 22:09:41 -0700" ~{6492}
S: 10 BAD Error in IMAP command APPEND: Expected '{'
S: 492} BAD Error in IMAP command : Unknown command.

This error occurs about 340 messages in.  If I switch to using regular  
literals, this error does not occur.  I can verify that neither the  
12:38:21 message nor the 22:09:41 message alone is broken (I can put  
just these two in a file and import and it is successful).

I can provide the mbox file privately, if needed.

michael