Email Migration
240 mailboxes off ageing Exchange in a single weekend
An on-premises Exchange 2013 server past end of support, six depots, and a dispatch system hard-wired to the old SMTP relay.
- Client
- Regional logistics group
- Sector
- Logistics & transport
- Year
- 2025
- Service
- Email Migration
- 240
- Mailboxes migrated
- 18 min
- Cutover window
- 0
- Lost items at reconciliation
Engagement
Stack involved
- Exchange 2013
- Exchange Online
- Entra Connect
- Intune
- PowerShell
The situation
The Exchange server had been out of support for two years and was the single point of failure for six depots. A dispatch application relayed through it using an unauthenticated connector nobody had documented, and two of the depots ran on connections too slow to move historic mail during a weekend window.
What we did
- 01
Full discovery of mailboxes, shared mailboxes, delegations and the undocumented relay dependencies.
- 02
Historic mail pre-staged over eleven days, throttled per site so the slow depot links stayed usable in working hours.
- 03
Dispatch system re-pointed to an authenticated Exchange Online connector and tested against a staging tenant before the window.
- 04
TTL on MX records lowered 72 hours ahead; cutover run against the runbook with a two-person verification step at each stage.
- 05
Item-count reconciliation per mailbox, with an exceptions list produced and cleared before sign-off.
The outcome
The cutover ran on a Saturday evening and completed in 18 minutes. Item-count reconciliation matched across all 240 mailboxes. The dispatch integration ran through Monday’s peak without a queued message, and the on-premises server was decommissioned the following month.
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ReadTell us what is breaking.
A short call, an honest read on whether we are the right fit, and a fixed-price proposal after discovery. No obligation and no sales sequence afterwards.