M365 Migration Checklist

Here is a useful checklist we have complied to plan for a migration to M365 (Office 365). This has an emphasis on Exchange Online, but will also provide the basics for all other Office 365 services:

1. Business case approved for license costs and implementation costs

2. Users grouped into ‘licensing buckets’ depending on use cases & requirements (e.g. 20% E5, 80% E3)

3. Ensure users on recent versions of Office (2016 or 2019)

4. Audit all Outlook plugins and ensure these are upgraded to the latest versions, matching the outlook version, and fully supported

5. Ensure users use Outlook cached mode (including terminal servers/Citrix with FSLogix/similar)

6. Install latest version of Onedrive client (not groove.exe)

7. Audit & upgrade PC OS & hardware if required

8. Assess readiness for using Windows 10 Azure AD domain joined devices & plan strategy for migrating GPOs to Intune (tool for this)

9. Ensure mobile devices supported by Intune & define Intune policies

10. Audit AD & Exchange architecture (e.g. forests, Exchange orgs)

11. Plan deployment of AADConnect, choose authentication method (e.g. PTA, PHA, Federation)

12. Choose source anchor for AADConnect.

13. Ensure all shared mailboxes are only accessed by a maximum of 20 people concurrently

14. Audit number/size of user mailboxes - need to be less than 100GB

15. Check shared mailboxes (free license) need to be less than 50GB, or less than 100GB if licensed as user mailboxes

16. Audit email archive solution usage (inc PSTs) and adjust plans accordingly – consider importing to Exchange Online Archive, does any archived email need to be re-inflated?

17. Audit mailflow requirements (e.g. transport rules, anything complex like SMTP namespace sharing), plan for target solution

18. Gather email security requirements, e.g. security gateways, DLP, encryption, plan for target solution

19. Assess GAL requirements, any existing GAL sync, MIM/FIM, plan target solution

20. Assess calendar federation requirements, any existing org relationships? plan target solution

21. Map all permissions across all mailboxes and group into migration batches that maintain access

22. Audit public folder use, assess readiness for migration to O365 Groups

23. Estimate projected WAN usage and ensure sufficient available bandwidth for all sites

24. Ensure web proxy is bypassed for O365 URLs & IPs (can use PAC file generator to assist)

25. Ensure Firewall allows traffic to O365, including URL filtering as many endpoints are CDNs

26. Hybrid mode - Check local Exchange server’s URL settings with powershell & remediate if required to ensure functional autodiscover (Oabvirtualdirectory & WebservicesVirtualdirectory, OWAVirtualDirectory, EcpVirtualDirectory, ActiveSyncVirtualDirectory)

27. Ensure Autodiscover & internal/public DNS is configured correctly for each domain

28. Make sure we use geographically local DNS servers for all offices

29. Ensure any public facing websites matching the domain of a primary SMTP domain have TLS certs installed – avoid Autodiscover delays contacting HTTPS://<domain>

30. Audit fileserver usage, permissions structures for feasibility of migration to Sharepoint Online and/or Onedrive, plan target solution

31. Budget for migration tools such as Quest, Sharegate, Bititan, Code2

32. Assess readiness to use Onedrive folder redirection for desktop/my documents (Known Folder Move), plan target solution

33. Assess DLP requirements, plan target solution

34. Capture data retention requirements, plan target solution

35. Capture data residency requirements, choose tenant region and assess potential use of Multi-geo

36. Assess Conditional Access Policy (inc MFA) requirements, plan target solution

37. Assess readiness to migrate telephony to SfB or Teams

38. Gather SfB/Teams conferencing requirements, plan target solution

39. Gather SfB/Teams security requirements, plan target solution