How to Migrate from Microsoft 365 to PolarisMail
Whether you’re a reseller preparing a client’s Microsoft 365 domain for migration, or you’re moving your own mailbox, Microsoft 365 migrates differently than IMAP-based providers. Instead of a two-step process split across your DNS cutover, Microsoft 365 migrates in a single step, and it happens after your MX records already point to us, not before.
This applies whether you’re a reseller preparing a client’s migration or migrating your own mailbox. This is a PST-based migration, not an IMAP one, so the general migration guide in our wiki doesn’t apply here. Follow the steps below instead, and reach out through the Support Portal when you’re ready to send your files.
Which tier matches your Microsoft 365 usage?
Microsoft 365 covers a lot of ground beyond just Outlook: Teams, SharePoint, OneDrive, Word/Excel/PowerPoint Online. Here’s how the pieces you actually use line up against our tiers:
✗ Not available
Italics = partial support
| If you use… | The equivalent is… | Basic | Enhanced | OEX |
|---|---|---|---|---|
| Outlook (email) | Webmail | ✓ | ✓ | ✓ |
| Outlook calendar & contacts sync | CalDAV/CardDAV or native sync | Webmail only | Via free plugin | ✓ native, no plugin |
| Outlook Mobile (calendar & contacts on phone) | Mobile device sync | Email only | ✓ ActiveSync | ✓ native, via MAPI |
| Microsoft Teams chat | Live Chat in Webmail | ✓ | ✓ | ✗ |
| Microsoft Teams meetings | Video calls in Webmail | ✓ | ✓ | ✗ |
| Microsoft 365 Groups | Distribution lists | ✓ | ✓ | ✓ |
| Shared team calendars & files (SharePoint/Teams) | Advanced groupware | Shared folders only | ✓ | Native client sync only |
| Word, Excel, PowerPoint Online (co-authoring) | Office Docs | View, upload, share only | ✓ | ✗ |
| OneDrive file storage | Personal Drive | 5 GB | 15 GB | ✗ |
If your team mostly lives in Outlook for email, Basic covers that. If you need calendar and contacts synced across devices, or real-time co-authoring on documents, Enhanced is the closer match. If native Outlook connectivity without a plugin is the priority and you don’t rely on chat, video calls, or Office Docs, OEX is built specifically for that. As with the other tiers, mailboxes can be mixed under the same domain, so different users can land on whichever tier matches what they actually use.
How the migration works
Unlike IMAP-based providers, we can’t run two passes of a PST import, so there’s no “before and after” step here. Instead, the whole thing happens in order, after your domain is already pointed at us:
- Set up your DNS so the domain’s MX records (and related records) point to PolarisMail first (see the Wiki guide here).
- Export the mailbox to a PST file from Outlook.
- Upload the PST file to a shared file drive (whatever you already use for large file transfers).
- Send us the link through a support ticket, and we’ll take it from there.
DNS goes first, not last. This is the opposite order from IMAP-based migrations. Since we only get one import per mailbox, don’t switch your MX records until you’re ready to export and hand off the PST – and don’t send the PST before the domain is pointed to us.
Exporting a mailbox to PST
- Open Outlook (desktop).
- Go to File → Open & Export → Import/Export.
- Choose Export to a file, then Outlook Data File (.pst).
- Select the mailbox (or specific folders) to export.
- Save the .pst file somewhere you can upload it from.
Exact wording can vary slightly by Outlook version. If you’re exporting many mailboxes for a client, check with your Microsoft 365 admin about bulk export options through the Microsoft Purview compliance portal; this typically requires an eDiscovery Manager role and isn’t a self-serve setting on every tenant.
Since there’s only one import per mailbox, keeping each migration batch to a manageable number of mailboxes still matters: if a PST file needs to be re-sent (for example, if it’s corrupted or incomplete), a small batch gets fixed and re-processed much faster than one bundled with hundreds of other mailboxes.
What happens next
Once your DNS is pointed to us and you have a PST file ready, upload it to a shared file drive and open a ticket through the Support Portal with the link.
Start your 30-day trial. Migration included.