10 things to watch when migrating to Microsoft 365

Migrating to Microsoft 365 isn't "just moving email." Done right, it's a platform shift that grows enterprise productivity, security and device management. Planned wrong, it can cause weeks of downtime and data loss.

There are 10 topics always overlooked or underestimated in migration projects. Here they all are.

1. Choose the right license — consider Premium first

Business Basic is the cheapest but excludes most security features. Business Premium includes Office apps + Entra ID P1 + Intune + Defender; those who pick Basic without knowing this difference end up buying add-ons one by one later. For most SMBs, Premium is the right choice.

2. Map DNS and MX records before the migration

Who manages your current DNS? Do you have the control-panel password? What about MX, SPF, DKIM and DMARC records? Starting to look for these answers on cutover night is a disaster. List them and confirm access.

3. Design the identity architecture in advance

Do you have an on-premises Active Directory? Do usernames (UPN) match email addresses? Will you do a hybrid join or go cloud-only? These are very hard to change after migration — decide at the start.

4. Calculate mailbox size and the migration window

If each of 20 users has 30 GB of mail, you'll need to push 600 GB of data out over your internet link. On constrained bandwidth this takes days. Choose between cutover, IMAP, hybrid or a third-party tool accordingly.

5. Inventory public folders, shared mailboxes and distribution lists

In most projects assumed to be "just individual mailboxes," shared mailboxes and old public folders turn up as surprises. If they're skipped during migration, users will call you back.

6. Clarify the OneDrive / SharePoint strategy

Saying "let's dump all files into OneDrive" isn't enough. Which content is personal (OneDrive), which is team (SharePoint/Teams), which is corporate (a central SharePoint site)? Without this distinction, files scatter and no one can find them.

7. Make MFA mandatory along with the migration

After migration, mail is in the cloud and an easy target for bad actors. Don't put off MFA with a "we'll add it later" mindset — make it mandatory. The migration moment is the best opportunity to enforce it.

8. Enroll devices in Intune

Not using Intune when you have a Premium license is a big loss. Bring devices into Intune along with the migration and apply conditional-access policies.

9. Test Outlook profiles and clients

Old Outlook versions, third-party add-ins, clients that don't support modern auth — they all cause problems. Test with a pilot group, build an issue list, then roll out.

10. Plan user training and communication

Don't just send a "new password" and walk away. Prepare short videos or guides explaining what to do a week before, on the day of, and after the migration. Your help-desk load drops tenfold.

At Bilgi Teknoloji we manage Microsoft 365 migrations by running these 10 topics as a checklist. You can schedule a free assessment call with our certified engineers.