caldav support?

I'd like to be able to initiate or accept caldav (iCal) meeting invitations from my inmotion hosted email address. That is, when I create an invitation on my calendar in iOS or iCal on the mac and send it to an invitee, I'd like the "from" address to be my email address hosted by inmotion. I'd also like to be able to accept invitations and have the acceptance message come from the same email address.

Right now, I'm stuck with doing this from my gmail calendar. That calendar supports caldav, so I can initiate and accept invitations from my devices using my gmail address -- but others see them as coming from my personal email address. In some cases, I can't accept others' invitations sent to my inmotion hosted address, because they can only be accepted by the recipient they're intended for, and inmotion provides no way to accept invitations.

Until inmotion decides to support caldav, Is there a way to use an external service for this -- e.g., a caldav hosting service? I've tried fruux, which works sort of, but my invitees see the invite coming from fruux.com, even though my inmotion hosted email address is listed as the meeting organizer.