Many consultants throw the baby out with the bathwater...and they often have justifiable reasons for doing so. When you don't know what the other consultants have done along the way, many a consultant have found that a new server/a new domain controller means that you start fresh. The process included determining what ya got, attempting to figure out how someone (badly) set it up before, recreating it with your new domain plan, ensuring you ask the boss if there are any things he does uniquely that he's forgotten to tell you (until you find out after the domain cut over) and you soothe any ruffled feathers after the fact.
If you do trust the domain (you set it up the last time) I'd still recommend an official AD migration.
But we need to understand what we got.
So first we read:
In my testbed, we have less than 25 users but remember Essentials role (not the SKU but the role) is not limited to 25 users. In fact it can go as high as 100 with 200 devices. So if you are thinking about an existing SBS domain with greater than 25 users and think that you can't use Essentials you can- just as the role on the normal server, not on the sku. Keep in mind that in either the sku or the role, you will need Exchange cals and Server cals to properly license. And these days because I really do like offering up RDS gateway role access to iPads and what not, plan on RDS cals. To help with the sticker shock on all of these things you have to buy that you didn't have to before, plan on 3 year spread payments via Open license. It helps the medicine go down better.
We have a single Exchange server (Exchange 2007) and a typical SMB firewall. No TMG here (and it's discontinued anyway so it would be irrelevant regardless)
Our mail hygiene is an external cloud product (see I use cloud!) of www.ExchangeDefender.com which also provides the network during the time of migration a hold and storage of email should (heaven forbid) anything happen in the process.
There are no Blackberry devices but there are obviously many iPhones and iPads as well as one Android device.
There is a email footer software called PolicyPatrol (http://www.policypatrol.com/ - sign of the times they now support both Office 365 as well as Google apps to add email disclaimer signatures). This email footer software adds the (annoying but required) tax information signature at the bottom of our emails as well as normal blurbs when the email does not contain tax information (the software is triggered by key words and works very nicely).
We have a backup solution - and have tested it.
In my instance, the Essentials server will implement the Application Request routing (ARR) that will allow for the ability to handle the 443 for both the remote web access as well as Exchange/OWA. We won't have TMG handling this process as we don't have a TMG server.
In our instance we'll me moving server roles and duties off of the SBS 2008 server and reusing that server for alternative needs, it's also the main non domain joined hyperV hoster and while I'm not comfy with it being in the main position, it still has some life left to be a secondary server that I won't trust as much as I use to.
Next step discovery of the network...
Blogging my way (starting over) through a proof of concept migration from SBS 2008 to Essentials 2012 R2 series will be a SMB kitchen project whitepaper. More about the SMBKitchen project at - http://www.thirdtier.net/enterprise-solutions-for-small-business