Can I use Office365 e-mail to a subdomain while keeping my hosted IMAP in the primary domain - requires multiple MX records?

One of our company entities is currently using the hosted IMAP e-mailed provided for free as a part of their website hosting account.  I really want to move them to Office365, but the price difference - from "free" to $$$ - is making it a hard sell.  The companies has a group of employees - 30-40 - that really can get by with the IMAP hosting.  Another smaller group of 10 or so employees would really benefit from the features of Office365 hosted e-mail.  My thought is keep email to @mydomain.com pointing to the IMAP server via its MX record.  Setup Office365 to a subdomain @admin.mydomain.com and have its own MX record setup.  This seems possible, but I don't exactly know how Office365 setup will go in a subdomain.  Also, If I setup Office365 in this subdomain environment, would it be possible to move it to @mydomain.com if we ever reached a point where we were OK with paying for O365 subscriptions for all of the users?
Lew NixAsked:
Who is Participating?

[Product update] Infrastructure Analysis Tool is now available with Business Accounts.Learn More

x
I wear a lot of hats...

"The solutions and answers provided on Experts Exchange have been extremely helpful to me over the last few years. I wear a lot of hats - Developer, Database Administrator, Help Desk, etc., so I know a lot of things but not a lot about one thing. Experts Exchange gives me answers from people who do know a lot about one thing, in a easy to use platform." -Todd S.

CESNetwork AdministratorCommented:
I don't see anything wrong with your idea.  The MX subdomains should work fine; people just aren't used to having that type of email address.

It's all DNS so as longs as O365 lets you set up the subdomain you should have no problems.  This KB might help for that:

https://technet.microsoft.com/en-us/library/dn736027(v=exchg.150).aspx

To answer the second part of your question, you may need to do an export to PST and import into new mailboxes

Experts Exchange Solution brought to you by

Your issues matter to us.

Facing a tech roadblock? Get the help and guidance you need from experienced professionals who care. Ask your question anytime, anywhere, with no hassle.

Start your 7-day free trial
It's more than this solution.Get answers and train to solve all your tech problems - anytime, anywhere.Try it for free Edge Out The Competitionfor your dream job with proven skills and certifications.Get started today Stand Outas the employee with proven skills.Start learning today for free Move Your Career Forwardwith certification training in the latest technologies.Start your trial today
Office 365

From novice to tech pro — start learning today.