Did some imapsync from my providers imap server to my NethServer and it worked as expected. Mails are there in roundcube and webtop and everything seems fine. This is what I did:
yum -y install imapsync imapsync --host1 providerimapserver --port1 993 --user1 name@provider.at --password1 PASSWORD1 --ssl1 --host2 localhost --port1 993 --user2 name@domain.local --password2 PASWORD2 --ssl2
dovecot dsync may also be interesting…as we won’t need an extra package.