Co-existance of Groupwise 2014.2 1 and 2018.2

Hi All,

It's been a while since I have been on the forums as well as done a Groupwise system

My client has a 2014.2 system on SLES 12 and needs to install a fresh SLES 15 in order to move to Groupwise 2018.2

I was thinking of adding a secondary domain and post office on the SLES 15 server, move all the users to the new system. Making the new system the primary domain and then upgrading the new server to GW 2018.2.

My question is can both systems talk to each other as I was hoping then to migrate the GWIA, Web Access and Mobility piece by piece to keep downtime to the minimum.