it's sad that after updating i-mscp to rc2.1 all roundcube sql tables were flushed, so that every identity and every address gets lost.
a workaround for that is dumping all roundcube_* tables from the old imscp-database (the pre-updated one) with (for example) phpmyadmin and edit the dump by search-n-replace all table names with "roundcube_" eliminate this prefix and put the dump back again to the new imscp_roundcube database.
i think this process should be done automatically by the install-script.
this couldn't be that difficult.
greeting, bomas