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Migrate from Microsoft 365 to MailSprout

Your old emails come with you. This guide walks you through copying every message from your Microsoft 365 / Outlook mailbox to MailSprout, then flipping your domain's MX records so new mail flows here. About 30 minutes per account, most of which is sit-and-wait while imapsync runs.

Before you start

  • Your Microsoft 365 sign-in (with admin rights if you're on a business tenant. See Step 2).
  • A MailSprout account already created with the same address (create it in the dashboard).
  • Your domain's MX records currently pointed at Microsoft (we change them last).
Two-step model: first copy old email to MailSprout while Microsoft still receives new mail (everyone keeps working). Then change the MX records to cut over. Then run the sync one more time to sweep up anything that arrived during the cutover. Zero downtime, zero lost mail.
1

Create the destination account in MailSprout

In your MailSprout dashboard, open the relevant domain and click Add account. Type the same name (the bit before the @) you have in Microsoft 365. If your old address was you@yourdomain.com, type you. Go to the account page in your MailSprout dashboard. In the Bring over old emailsection, you'll find the destination server credentials you need.

MailSprout will generate a strong password and show it to you once. Save it; you'll need it in Step 3.

2

Enable IMAP and create an App Password

Microsoft 365 disables IMAP for most tenants by default and modern security blocks normal password login from third-party tools. You need to do two things:

  1. Enable IMAP on the mailbox.
    • Personal accounts (outlook.com, hotmail.com, live.com): IMAP is on by default. Skip this part.
    • Business tenants: an admin signs in to admin.microsoft.com (opens in a new tab) → Users → pick the user → Mail tab → Manage email apps → tick IMAP.
  2. Create an app password.
Microsoft 365 'Add a method' dialog with 'App password' selected
On the Add a method page, pick App password and click Add.Source: Microsoft Support (opens in a new tab)
App passwords require Security Defaults or Conditional Access to allow them. If your tenant blocks app passwords, an admin can enable per-user app passwords or temporarily grant a Conditional Access exception for the migration. Email support@mailsprout.ioif you're stuck; we've seen most of the tenant configurations.
3

Run the migration with imapsync

Go to the imapsync free web app: imapsync.lamiral.info/X/ (opens in a new tab). Fill in your credentials and click Start.

Fill in the form with two sets of credentials:

Source (Microsoft 365)

  • Host: outlook.office365.com
  • Port: 993 (SSL)
  • User: your full Microsoft 365 email
  • Password: the App Password from Step 2

Destination (MailSprout)

  • Host: fusion.mxrouting.net
  • Port: 993 (SSL)
  • User: the same email address
  • Password: the MailSprout password from Step 1

Click Start. imapsync copies every folder, every message, every flag (read/unread, flagged, categories). For an average 10k-message inbox, plan on ~30 minutes. You can close the browser tab; the job runs server-side and emails you when it's done.

4

Verify the migration looks right

Set up your MailSprout account on a device (scan the QR code on the account page with your iPhone Camera). Open Apple Mail (or Outlook on the same device pointed at the MailSprout server) and confirm your old folders and messages are there.

Do this beforechanging MX records. If anything looks wrong, fix it now; there's no rush yet because Microsoft is still receiving your live mail.

5

Cut over MX records

Open your registrar's DNS panel and replace the Microsoft MX records with MailSprout's. Use one of our registrar tutorials:

Old Microsoft MX records look like yourdomain-com.mail.protection.outlook.com. Remove those; add MailSprout's fusion.mxrouting.net (priority 10) and fusion-relay.mxrouting.net (priority 20), plus the SPF, DKIM, and DMARC records from the MailSprout dashboard.

DNS isn't instant. Some senders may still try Microsoft for up to a few hours after you change MX. That's why Step 6 exists, to sweep up anything that arrived at Microsoft during the cutover.
6

Run imapsync one more time

About an hour after the MX change, go back to imapsync and re-run with the same credentials. It only copies new messages (skips what's already on the destination), so this is fast.

7

Cancel Microsoft 365 (when you're sure)

Wait at least a week so you can re-run imapsync if a stray message lands at Microsoft. Then in the admin center: Billing → Your products → pick the subscription → Cancel subscription.

Troubleshooting

imapsync says authentication failed for the Microsoft account.
The App Password is wrong (re-generate in Step 2), IMAP isn't enabled on the mailbox, or your tenant's Conditional Access policy blocks IMAP. The fastest unblock is for an admin to grant a temporary exception for migration.
I see folders called "Archive", "Conversation History", etc. that I don't recognize.
Outlook creates system folders that don't show in its UI. imapsync copies them faithfully. You can hide or delete them in Apple Mail / your new client.
Will Teams, OneDrive, SharePoint come with me?
No.MailSprout is email only. If you're using the rest of Microsoft 365 actively, you may want to keep that subscription separately and just point MX to MailSprout.
I changed MX but new mail still arrives at Microsoft.
Wait up to an hour for DNS to propagate. Check current MX state at mxtoolbox.com (opens in a new tab); if it still shows *.protection.outlook.com, the registrar hasn't propagated yet.

Set up your domain first

GoDaddy→

The #1 registrar by market share. Most small businesses start here.

Namecheap→

Popular among indie founders and developers.

Cloudflare→

Power-user favorite. DNS panel is the cleanest in the business.

Porkbun→

Indie-hacker darling. Fast, cheap, fair pricing.

Squarespace Domains→

Includes former Google Domains customers who got migrated here.

Hover→

Long-time favorite of founders and writers.

Stuck on a step?

Email support@mailsprout.io with the step number and a screenshot. We reply same day.