SHAREGATE MAILBOX MIGRATION

Prepare the mailbox mapping before Copy mailboxes.

Use the six-column ShareGate mailbox format so every source mailbox has an explicit destination.

HOW TO PREPARE IT

Keep the preparation simple

01Download templateStart with the six ShareGate mailbox columns.

02Fill source and targetUse Microsoft 365 object IDs, names and email addresses.

03Check itOpselith validates GUIDs, emails and duplicates.

04Import itUse the CSV in Copy mailboxes or ShareGate PowerShell.

WHAT TO KNOW

Before you start

PowerShell licensingShareGate PowerShell integration requires Migrate Pro or Enterprise.

Explicit matchingOpselith requires all six fields so the mailbox match is clear before import.

Review after importShareGate can show warnings for uncertain or unmapped recipients; review them before copying.

No migration from OpselithOpselith only prepares and checks the file.

COMMON QUESTIONS

Quick answers

Can ShareGate export a template?

Yes. ShareGate can export mailbox mappings, and its documentation also defines the six-column structure for manually created CSV files.

Do I need object IDs?

Opselith requires the source and destination user IDs to make the mapping explicit and reduce ambiguous matches.

Does this migrate Gmail too?

ShareGate supports Google Workspace Gmail as a source for Copy mailboxes, but Opselith’s current workspace focuses on explicit Microsoft 365-style source and destination mappings.

PREPARE THE FILE

Use Opselith for the mapping work

Choose Mailboxes in the ShareGate workspace, fill the template, check it, and download the import-ready CSV.

Prepare mailbox mapping →All migration workspaces

Vendor behavior checked against ShareGate: Import-MailboxMappings. Opselith is independent and not affiliated with the vendor.