M365 Tenant-to-Tenant Migration — Şirket Birleşmesi Sonrası

“Başka Firmayı Satın Aldık, Onların M365 Tenant’ını Taşıyacağız”

Holding yeni şirket satın aldı. İki M365 tenant:

• Ana firma: firma.com.tr (400 user)
• Satın alınan: firmaalt.com.tr (80 user)

Hedef: firmaalt.com.tr tenant’ındaki 80 user + data → firma.com.tr’ye.

Migration Seçenekleri

Native Microsoft: MOVE Beta + Cross-Tenant User Data Migration

M365 Admin Center’da “Cross-tenant migration” (2023+ preview):

• Mailbox migration native
• OneDrive migration native
• Teams + SharePoint henüz kısıtlı

3rd Party Tools

• Quest On Demand Migration — kapsamlı, pahalı
• BitTitan MigrationWiz — popüler, kullanıcı başına ücret
• SkyKick — SMB’ye yönelik

Enterprise büyük tenant’larda 3rd party, küçükte native.

Hızlı Çözüm (TL;DR)

Basit senaryo (sadece mailbox):

1. Hedef tenant’ta kullanıcı hesapları aç (AD sync veya manuel)
2. Source tenant’ta mailbox migration batch
3. IMAP migration veya native cross-tenant
4. DNS MX record değişimi → mail artık hedef tenant’a düşer
5. 30 gün cutover + decommission source tenant

10:00 — Pre-Migration

Hedef Tenant’ta Kullanıcı Hazırlığı

Her source user için hedef tenant’ta:

• Hesap oluştur (CSV ile bulk)
• Lisans ata
• Mailbox provisioning (boş)

# Hedef tenant'ta
Connect-MsolService

Import-Csv source-users.csv | ForEach-Object {
    $upn = $_.DisplayName -replace "\s",""
    $upn = "$upn@firma.com.tr"
    
    New-MsolUser `
        -UserPrincipalName $upn `
        -DisplayName $_.DisplayName `
        -LicenseAssignment "firma:ENTERPRISEPACK"
}

Domain Strategy

İki seçenek:

• Retain old domain: firmaalt.com.tr hedef tenant’a taşı (verify + migrate)
• Retire old domain: Kullanıcı address değişir ad.soyad@firma.com.tr

Retain → mail trafiği kesintisiz. Retire → alias değişimi external contact’lara bilgi.

10:30 — Cross-Tenant User Data Migration (Native)

Microsoft’un yeni native çözümü. Prerequisites:

• Both tenants consent (accept migration agreement)
• Azure AD B2B collaboration enabled
• Scheduled Migration batch hedef tenant’ta

Admin Center > Setup > Microsoft Cross-Tenant User Data Migration:

📸 Ekran 1 — Cross-tenant setup
Source tenant ID
Target tenant ID
Trust agreement — her iki taraf consent
Migration batch create
Users CSV upload

Scheduled migration overnight. Delta sync cutover gün.

10:45 — Mailbox Migration — Classic

3rd party / IMAP ile:

PowerShell (Native M365 to M365)

New-MigrationBatch `
    -Name "T2T-Batch-1" `
    -SourceEndpoint (New-MigrationEndpoint -Name "Source-Tenant" -RemoteServer outlook.office365.com -Credentials (Get-Credential)) `
    -CSVData (Get-Content users.csv -Encoding Byte) `
    -TargetDeliveryDomain "firma.mail.onmicrosoft.com" `
    -AutoStart

CSV format:

EmailAddress
user1@firmaalt.com.tr
user2@firmaalt.com.tr
...

11:00 — OneDrive / SharePoint Migration

SharePoint Migration Tool (SPMT) — Microsoft

SharePoint Admin Center > Migration > OneDrive/SharePoint

• Source: Old tenant user’s OneDrive
• Destination: Target user OneDrive
• Incremental migration

SPMT CSV-based, bulk migration.

Content Considerations

• Permissions: External share link’ler yeniden tanımlanmalı
• File history: Version history korunur
• Metadata: Custom columns migrate
• Size: 10+ TB migration günler alır

11:30 — Teams Migration

Teams native cross-tenant kısıtlı. 3rd party (Quest, AvePoint) daha iyi:

• Channels + messages
• Files (SharePoint backed)
• Apps + tabs

Native:

New-CsTeamsMigrationRequest -SourceTenant X -TargetTenant Y

Limitation: Public channel message history bazen kayıp.

12:00 — DNS Cutover

Tüm data migrate edildi → MX kaydı değişimi:

Source tenant (firmaalt.com.tr):

• MX: firmaalt-com-tr.mail.protection.outlook.com (Microsoft 365 default)

Target tenant:

• firmaalt.com.tr domain add
• Microsoft TXT record verify
• MX: firma-com-tr.mail.protection.outlook.com (hedef tenant)

DNS propagation 1-24 saat.

Yaygın Problemler

Mailbox Migration Slow

Network bandwidth kısıtlı. Source tenant’tan hedefe M365 to M365 migration Microsoft throttle uygular — günde 300-1000 mailbox pace. Büyük batch’lerde hafta sürebilir.

Attribute Loss

Migration sonrası attribute kaybı:

• manager
• department
• employeeId

AD Connect her iki tarafta ise sync korunur. Cloud-only tenant’ta manuel remap.

License Cost Overlap

Hem source tenant hem target tenant aynı user için lisans taşır geçiş döneminde. 30-60 gün süreyle iki kat lisans maliyeti. Planlamada bütçe.

İlgili Rehberler

• Azure AD Connect sync
• Exchange Hybrid HCW

M365 migration (tenant-to-tenant, on-prem to cloud) uzman destek? Teknik görüşme.