Judging by what I see, you must be using BincIMAP as your IMAP server. From a former frustrated BincIMAP user I can tell you that unfortunately, many of these issues are due to BincIMAP and not RoundCube. I wish I had better news...
I struggled with a BincIMAP server for a while and when faced with all its shortcomings I ended up converting that server to Courier. I had to modify my user administration scripts to add/change a database as well as qmail's files, but in the end it's a lot more stable/functional.
I also had a couple comments for other issues you noticed.
E-Mail::List View
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2. BincIMAP issue - Though at some point this had been fixed. (BincIMAP doesn't understand UTF-8 encoding) - See
http://trac.roundcube.net/trac.cgi/ticket/14838553. BincIMAP issue - BincIMAP does not support SORT command
E-Mail::Message View
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1. BincIMAP issue - BincIMAP doesn't like the new message retrieval method used recently. (See
http://trac.roundcube.net/trac.cgi/ticket/1484070 )
5. Probably related to #1
E-Mail::Composing
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2. This is a PHP install/Server issue.
6.
http://trac.roundcube.net/trac.cgi/ticket/1484158 - Should be fixed in rev 405
7. See 6
[2006/12/18 9:25am] Edited: fixed typo, meant to say BincIMAP doesn't support the SORT command. I had mistyped SEARCH instead (oops)