Syncing email activity between 2 servers

Hi there,

We are trying to find a way to sync email activity between two (2) servers.

We have a US-based VPS, which is our mail server, as well as a server in our Africa office. Because internet connection is frequently disrupted in our Africa office, we'd like to use our Africa server to allow staff to send emails internally while connection is down. When connection returns, we'd like any email activity to be synced with our US-based server.

Is there any way to do this - thx !