HowTos/Advanced imapsync
From Scalix Wiki
When migrating mailboxes via imapsync, some thunderbird users' mailboxes may fail to migrate if they have flags set that are not recognized by scalix server.
In this event, you can use the parameter --regexflag to reset flagging.
The parameter --regexflag 's/^.*$/Seen/g' will set all messages to read and remove all other flags.
