Hi haraldc,
Currently we only support
forwarding of mykeep.net/op-i.me email, sorry

Not ruling out that we add support for custom domains later. But for now our backend infrastructure only handle unit-domains. You can of course however use our outgoing relay to send email with any sender address.
To configure your unit to use the Openproducts mail relay just use the admin UI, E-MAIL CONFIGURATION, Mail server config
Check send and receive checkboxes.
This will configure our relay to accept all mail that is sent to your device-name addresses. For example if your device name is
coolname,mykeep.net all emails sent as
name@coolname.mykeep.net will be accepted by our relay and forwarded to your local unit on port 2525.
For this to work two things must be in place.
1. You have to have OpenProducts dyndns service enabled and it has to correctly point at your public IP-number.
2. internet traffic to this IP on port 2525 has to reach your unit. This could need some firewall forwarding in any routers etc.
I hope this somewhat answers your question. If not please get back! All feedback is always very welcome.
/Tor