O365 Migration: migrate Exchange mailboxes with a CSV file
Copy mail, contacts and calendars from each source mailbox to its destination mailbox, from a CSV of source and destination mailboxes.
The CSV
SourceMailbox,DestinationMailbox
jane.doe@contoso.com,jane.doe@fabrikam.com
john.smith@contoso.com,john.smith@fabrikam.comUse user principal names or e-mail addresses. The destination mailboxes must exist (users licensed for Exchange Online). Check confirms both mailboxes before you start.
What is copied
| Item | Details |
|---|---|
| Every folder and sub-folder. Inbox, Sent Items, Drafts and Archive map to their counterparts in any language. Messages keep their received and sent dates, read/unread state, flags, importance, categories and attachments. They arrive as received mail, not drafts; drafts stay drafts | |
| Contacts | The Contacts folder and contact folders, with names, companies, e-mail addresses, phone numbers and addresses |
| Calendars | The user's own calendars, with events and recurring series. Events are created without attendees, so nobody receives an invitation; the organizer and attendees are written at the top of each event |
Options
- Mail, Contacts, Calendars: choose what to copy.
- Skip Deleted Items and Junk Email: on by default.
- Only items since: a date, to leave old mail behind.
Running again
Every copied item is tagged with its source ID, so running the same list again only adds new items. Run once in advance, then again just before switching users over.
Not migrated
E-mails or calendar items attached to other messages, rules, shared and delegated calendars, archive mailboxes and public folders.
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Updated 2026-10-17