Changing Email Address Policies (remove old email address format)

Quick question,

I am trying to clean up our Exchange 2013 environment before going to O365, our company has some OLD Email Address Policies in place... the default, contains smtp addresses which is not a primary SMTP nor even in use. We also have the old X400 address in there.

I want to remove these, and apply... would this cause any issues, provided that no use has been using the email address or the X400 address? After applying, this will remove the addresses from the users mailboxes correct?

I know that after running the Office 365 hybrid config wizard we our tenant will be added to it, which is fine...

Anything Im overlooking? Any gotchas? Thanks in advance.
Christian HansUndecided... Asked:
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remove which ever you are not using.  Just create new policy as per your requirement and make it default.

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It costs you like nothing to maintain old addresses until all issued business cards rot away....
Christian HansUndecided... Author Commented:
So I guess if I were to create a new email address policy using only the domains that I want to keep, we will have issues with it applying against mailboxes that may have the " Automatically update email addresses based on the email address policy applied to this recipient " unchecked in cases such as users with duplicate names etc? Correct?
That software policy has nothing to do with real life policy and business cards. You can issue fresh email addresses using default policy, but you need to maintain old addresses for week-month-year-forever.
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