Although there is some overlap among these uninstall articles, it’s worth reading each for their individual contributions.
Upgrade Exchange 2003 to Exchange 2010 (part 1 and 2): https://www.simple-talk.com/sysadmin/exchange/upgrade-exchange-2003-to-exchange-2010/ and https://www.simple-talk.com/sysadmin/exchange/upgrade-exchange-2003-to-exchange-2010---part-ii/
Decommissioning Legacy Exchange Servers: http://blogs.technet.com/b/mspfe/archive/2015/08/26/decommissioning-legacy-exchange-servers.aspx
How to Remove the Last Legacy Exchange Server (2003) from an Organization: https://technet.microsoft.com/en-us/library/bb288905.aspx
How to remove Exchange Server 2003 from your computer: http://support2.microsoft.com/?kbid=833396
Removing the First Exchange 2003 Server (Part 1): http://www.msexchange.org/articles-tutorials/exchange-server-2003/migration-deployment/Removing-First-Exchange-2003-Server-Part1.html
Remove the Last Legacy Exchange Server from an Exchange 2010 Organization: https://technet.microsoft.com/en-us/library/gg576862.aspx
You receive a "c1034a7f" error message when you delete a mailbox store: "One or more users currently use this mailbox store": https://support.microsoft.com/en-us/kb/279202
Convert Recipient/Email Address Policies:
Upgrade the Default E-Mail Address Policy from LDAP Filters to OPATH Filters: https://technet.microsoft.com/en-us/library/Dd351283(v=EXCHG.141).aspx and ConvertFrom-LdapFilter.ps1 (Need help converting your LDAP filters to OPATH?): https://gallery.technet.microsoft.com/scriptcenter/7c04b866-f83d-4b34-98ec-f944811dd48d and Address List and EAP filter upgrades with Exchange Server 2007: http://blogs.technet.com/b/exchange/archive/2007/01/11/3397719.aspx
Check Your Legacy Exchange Servers for SMTP Usage Before Removing Them: http://exchangeserverpro.com/check-your-legacy-exchange-servers-for-smtp-usage-before-removing-them/ and Report Top Sender IP’s on Exchange Server 2010 using Log Parser: http://exchangeserverpro.com/exchange-2010-report-top-sender-ips-log-parser/
Replace Recipient Update Service (RUS) Upgrade Distribution Lists and Contacts:
PS > Get-DistributionGroup –ResultSize Unlimited | update-recipient
PS > Get-DistributionGroup –ResultSize Unlimited | Set-DistributionGroup –ForceUpgrade -RequireSenderAuthenticationEnabled $False
PS > Get-MailContact –ResultSize Unlimited | Update-Recipient
PS > Get-MailContact –ResultSize Unlimited | Set-MailContact -CustomAttribute1 "Ping" -Force
Update mail contacts to Exchange 2010 | Exchange DUDE: http://www.exchangedude.net/index.php/2012/04/update-mail-contacts-to-exchange-2010/
How to Remove Spaces From Recipient Aliases by Using the Exchange Management Shell: Exchange 2007 Help: https://technet.microsoft.com/en-us/library/bb851499(v=exchg.80).aspx
Exchange - Removing Illegal Alias Characters using PowerShell: https://www.mimecast.com/blog/2011/08/exchange-removing-illegal-alias-characters-using-powershell/
PFDAVAdmin Content Report : http://blogs.technet.com/b/exchange/archive/2006/02/01/418566.aspx
Organizational Forms Library: http://www.slipstick.com/exchange/2010-exs/organizational-forms-library-exchange-2010/
Check database client setting for default public folder server >Get-MailboxDatabase | Select name,server,PublicFolderDatabase | ft -a