I've recently had the same question with one of my customers.
They wanted the new site I was developing for them hosted on Adobe BC, but to keep all their emails with their existing Internet Service Provider.
I was given this link:
Step 3 Point 2 - "Pointing A-Records to your BC Site" - is what needs to happen.
This is what I did with my customer and they are now happily implementing email campaigns from Adobe BC even though their email accounts are hosted elsewhere.
Hope that helps.
Thanks for answering quckly Derek, so for what i understand...
we need to go to thier registrar, and redirect by an A record to the BC ip. so that way the MX wont be affected?
you see, i'm no "network ninja" if you know what i mean...
I'm not a "network ninja" either, but yes that is exactly what we did.
It has worked perfectly and none of my customers email accounts have be affected.
With best wishes for a successful website launch
Merci beaucoup monsieur!