In the first part of this series I had an overview of
Exchange migration which can be found here.

In the second part of these series I will provide more about
handling the transformation to UPN. When you decide to use e-mail addresses for
your UPN, you will need to make sure that you create the UPN from the used
e-mail address of the user. Although this may seem trivial it may not be.
Generally you will want to create the UPN from user’s alias attribute and the E-mail
domain. However alias attribute is populated only once during the mailbox
creation and administrator can change the mail address of the user after it has
been created. In order to identity these account we need a script to compare
these values. The script will basically do the following:

First read all the mailboxes in the organization and loop on
them. Please note that you will need to put resultsize unlimited parameter to
get the whole picture.

get-mailbox
-resultsize unlimited | foreach{

Then you would need to get the e-mail addresses of the user
inside the loop.

for ($i=0;$i -lt
$_.EmailAddresses.Count; $i++)

Once you have the list, you will go through the list looking
for address prefix SMTP which will give you the Primary SMTP address (Secondary
ones will be given by smtp). Some of the users may have empty Email addresses
so you need to check that condition also

$address =
$_.EmailAddresses[$i]

$a=$address.AddressString.ToString()

if
($address.PrefixString -eq "SMTP" -and $a.length -gt 0 -and $a.indexof("@")
-gt 0)

Now that you have found the address you need to store it to
be used after the loop.

$Primary=$a.substring(0,$a.indexof("@"))

Now lets check if this matches the alias attribute

if
([String]::Compare($_.Alias,$Primary,$True) -ne 0)

You will generally have the necessary plumbing to write the
results into a log file for easy consumption. The complete script can be found
as an attachment to the blog. The script is provided as is without any warranty
so use it at your own risk.

After you have identified these users you will need to
correct the alias attribute according to the primary SMTP address attribute.
The script for this is left as an exercise to the user.

You may be asking why we were so diligent about correcting
the alias attribute instead of setting the attribute through a script. The
reason is simple; writing scripts to touch large number of users requires
careful testing.

 So now we need to do
the following:

• 
  Create
  UPN suffixes: Creating UPN suffixes can easily be done through a single
  line of PowerShell. See here
  for more details.
• 
  Populate
  UPN prefix for each user: You can use ADModify tool to do
  this.

After this tasks your users will be able to use the same
e-mail address as their logon names.

Exchange migration has always been a topic of interest for
organizations. As more and more organizations depend on Exchange as their core
infrastructure downtime during upgrades have been noticeable by the clients and
need detailed planning. When there is a need to change the forest as a part of
this upgrade, the problem becomes a complex migration exercise.

Let’s take a hypothetical organization running Exchange 2007
which wants to move to Exchange 2010 in a new forest. For the sake of argument
lets say customer only wants to migrate exchange functionality to the new
forest and the old forest will remain where Exchange will be uninstalled. When
the number of clients involved is large, the mailbox move process can take
longer than the organization can tolerate downtime and coexistence is needed.
Coexistence can be defined as where you have 2 exchange organizations in 2
different forests and it acts like a single organization. Here are important
points to consider for kind of migration:

• 
  Mail
  flow: generally mail flow to and from Internet is done from the old
  organization during coexistence phase and mail between the organization is done
  with connectors in between.
• 
  Mail
  Access: For OWA users this will depend on where the mailbox is hosted at a
  given particular time. Exchange can provide redirection to the new environment,
  more on this later. For Outlook anywhere and ActiveSync users Autodiscover will
  need to be used in cross-forest configuration. In order for autodiscover to
  work you will need to have Outlook 2007 as a minimum on clients.
• 
  Availability:
  During coexistence you need to be able to query free/busy information. Exchange
  2010 supports several methods to get this information.

In order for these functions to work, you need do analysis
on source forest:

• 
  Single
  sign on: During coexistence you will need an entry point that can connect
  to both forests and would receive credentials from clients only once.
• 
  Account
  names: If customers are using Domainname\username format to logon, this
  will need to change when Exchange moves to the new forest. One way to solve
  this problem will be to use UPN. Users accessing old forest can start using UPN
  and the new forest will also have the same UPN but different forest name. Generally
  you would want to have UPN the same as the e-mail of the user.

This part clearly shows you need to have a lot of
preparation before you do the migration. We will focus on more details in later
series.