Add second email domain on SBS2011

I currently have an SBS2011 running in native mode (i.e. mx records>public IP, ptr -> and I have another two domains which I've added as authoritive domains and use SBS POP3 connector to get email for them.

Lately one of the domains has been losing email and I want to make it native with the current host as a backup using mx records. To do this I've thought of the following:

1. mx records -> public IP priority 0
    mx records -> current host priority 100
2. Change current host to act as backup in case public IP goes down and forward email to it once it comes back up.
3. Make PTR changes.

Now my main issues are 2 and 3. Will I need to use cpanel to create the exchange email accounts in the current host or will it keep the email in a general store and send them to the correct recipients once the public IP comes back on. And will I need to make any changes to PTR? Some say yes others just say that I need to make changes to the SPF to allow sending from public IP. Will multiple PTR pointing to one public IP mess things up?
Christos KassianidesTechnical Manager at DEXX ComputersAsked:
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Jose Gabriel Ortega CastroCEOCommented:
You already have the "accepted domain in the SBS"... So you just need to create the "email address policy in the ECP", and apply it for the others 2 domains (so the addresses are created as ALIAS) of the address that you already have, at least that you want to have 2 or 3 mailboxes for client, if that is the case you need to create all the "new users" to associate the email to that specific address.

What I'd do is to create an OU and create the new users there and apply an "email policy" to those users that are within a container (in this case OU), would be easier to manage and you just have to create the users in the correct OU for it.
Christos KassianidesTechnical Manager at DEXX ComputersAuthor Commented:
I already have everything setup on SBS2011 since I'm currently using this setup but with POP3 Connector. My main issue is how to make everything work without needing the POP3 Connector. (i.e. using mx records)

If the email host is currently receiving all the emails for domain2 (for example) and you are pulling them into Exchange using POP3, then there is nothing to do there.

Once you change the MX record so that the email for domain2, email will come to your SBS / Exchange server directly, unless it is unavailable or your connection goes down, in which case it will go to the email host again.  If your SBS / Exchange is already pulling those emails by POP3 it will continue to do so, generally getting nothing, but picking up anything that has gone there.

In terms of PTR record - if you don't have one setup already, then definitely get your ISP to add one for your hostname, but if that if already in place, nothing more to do there.

On the MX records, I would create a CName for Domain2 and domain3 ( or whatever) and point it to the A record for domain1's email host.  That way, you only have to change the IP in one place if it ever has to be updated.  Not a biggie either way, but definitely easier to manage that way.


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