Perhaps you have experienced a similar situation where you have found the following error:
apt-get upgrade Reading package lists... Done Building dependency tree Reading state information... Done Calculating upgrade... The following packages were automatically installed and are no longer required: libboost-filesystem1.55.0 libboost-system1.55.0 python-dialog Use 'apt-get autoremove' to remove them. Done The following packages have been kept back: kopano-backup kopano-client kopano-common kopano-contacts kopano-dagent kopano-gateway kopano-ical kopano-monitor kopano-presence kopano-search kopano-server kopano-server-packages kopano-spooler kopano-utils libkcserver0 libkcsoap0 libmapi1 php5-mapi python-mapi 0 upgraded, 0 newly installed, 0 to remove and 19 not upgraded.
This happens when you want to upgrade a package that has added new dependencies. Unlike yum, aptitude does not automatically install the new packages when upgrading. Instead, simply run
apt-get install packagename to resolve those dependencies and to upgrade the package. You can do this for all packages and in some situations this can upgrade the remaining packages as well.