Servers are both Debian 9. According to Debian package search they are version 2.5.10.
I need to find out if replication as described here Cyrus Documentation: Replication is encrypted over the WAN.
I know it can be with version 3+, as the replication protocol has been changed to use IMAP itself, which can be over SSL/TLS. That would however require a custom build on Debian.
I need to decide if I need to set up an IPSEC tunnel before I deploy it? or do I make a custom build?