No need to delete the question :-).
It is possible, though it’s not as simple as setting up a set of
MX DNS entries and calling it a day as you would if you were simply routing your e-mail through a single provider.
The actual term would be Split-Domain Routing, or SDR for short.
This type of setup requires that you setup a sub-domain and point it’s MX entry to the secondary mail server. You would then setup your actual domain on the secondary server to accept mail locally.
You would forward all mail from
firstname.lastname@example.org (Primary MX) to
email@example.com (Secondary MX) which would in turn forward that e-mail to the local account
firstname.lastname@example.org (which would reside on the Secondary MX server). So you’d have each e-mail bouncing from Point A, to Point B and then to Point C.
It seems simple enough, though you also have to account for potential flags. If e-mail is flagged at Point A, it’s not going to make it to Point B or Point C. Likewise, the same applies if this happens at Point B on the way to Point C.
You also have to account for outages and if your using a hosted solution, you have zero control over whether or not an e-mail delivery will be reattempted. So if Point A is down and no reattempt is made by the upstream mail server, it’s not going to make it to Point B or C.
Without fine-grained control over the mail server, no, this would not be possible as you would not be able to control local delivery. When you setup with a hosted solution, you forfeit any real control that you would have if you were running your own mail servers (which isn’t any more simple – it’s actually far more complex if you want a reliable solution).
Hope that at least helps a bit :-).