We use google apps for email, but it's all routed through a server of ours to have a backup and to be able to immediately migrate away should we have to: all ma

We use google apps for email, but it's all routed through a server of ours to have a backup and to be able to immediately migrate away should we have to: all mail that's sent to our domain and which is sent by us is not only in gmail but also in maildirs ready to be served over IMAP by changing one config file entry. All application mail is also sent over that server (a Ubuntu VM hosted on physical hardware we own). All installations of our product are hosted on VMs on more physical machines we own. Hence I voted the top option, even though we are also using Google for convenience.