How to Migrate From Microsoft 365: An Honest 2026 Guide

To migrate from Microsoft 365 to another email host, export each mailbox to a PST file, add the new mailbox to classic Outlook over IMAP, and drag your folders across. Direct password-based IMAP import usually fails because Microsoft has turned off basic authentication in Exchange Online. Then switch MX and Autodiscover records and remove the domain from your Microsoft 365 tenant.

That first step is the part most guides gloss over, so this article starts there. It then covers planning, the PST route step by step, DNS cutover, and the things that work differently once you leave Exchange.

Why a simple IMAP import usually fails

Most email importers, including the one built into Zomail, work by signing in to the old mailbox over IMAP with a username and password, then copying the folders. That works for Gmail (with an app password), Yahoo, cPanel hosting and almost any other IMAP server.

Microsoft 365 is different. Microsoft has retired basic authentication (username plus password) for IMAP and POP in Exchange Online, and personal Outlook.com accounts follow the same direction. Sign-in now requires OAuth, the "Sign in with Microsoft" flow. An importer that sends a password simply gets refused, even if the password is correct.

Zomail does not offer an OAuth import from Microsoft 365 yet. Rather than pretend otherwise, we recommend the route that works reliably today: PST export plus Outlook drag-and-drop. It is manual, but it is predictable and it keeps your folder structure.

Plan before you touch anything

A Microsoft 365 tenant often does more than email. Make a short inventory first:

Mailboxes and sizes. Note who has large mailboxes and archives (online archives need exporting too).
Shared mailboxes and distribution lists. Recreate them as shared mailboxes and groups in the new system. In Zomail, shared mailboxes work in webmail and the Zomail app, not in Outlook over IMAP.
Aliases such as info@ and sales@.
Things that send as your domain: scanners, CRMs, invoicing tools, website forms. Each needs new SMTP settings or an SPF update.
Teams, OneDrive and SharePoint. These are not email; plan their move (or decide to keep them) separately.
Licences. Keep Microsoft 365 licences active until the migration is verified. Microsoft keeps data only for a limited period after a subscription ends.

Then set up the new side: add your domain, create every mailbox and alias, and lower the TTL on your MX record a day before cutover. The getting started guide covers this in Zomail.

Step 1: Export each mailbox to PST

A PST file is Outlook's own data file. There are two common ways to get one.

Per user, in classic Outlook for Windows

Open Outlook with the Microsoft 365 account.
File → Open & Export → Import/Export → Export to a file → Outlook Data File (.pst).
Select the mailbox root, tick Include subfolders, choose a location and finish.

For many users, by an administrator

Microsoft 365 admins can export mailboxes to PST from the Microsoft Purview compliance portal using a content search or eDiscovery export. This avoids visiting every computer, though the tool and its menus change from time to time, so follow Microsoft's current documentation.

Classic Outlook for Windows is the most dependable tool for PST work. The "new Outlook" and Outlook for Mac handle data files differently, so if you can, do the export and import on a Windows PC with classic Outlook.

Step 2: Add the new mailbox to Outlook over IMAP

Now connect the destination mailbox to the same Outlook:

In Zomail, create an app password for the user (Settings → App passwords). Outlook will use it instead of the main password.
In Outlook, File → Add account, enter the new address, choose Advanced → Let me set up my account manually → IMAP.
Enter the settings:

Incoming (IMAP):  imap.zomail.io   port 993   SSL/TLS
Outgoing (SMTP):  smtp.zomail.io   port 465   SSL/TLS
                  (or port 587 with STARTTLS)
Username:         the full email address
Password:         the app password

Full screenshots are in connecting email apps.

Step 3: Open the PST and drag folders across

File → Open & Export → Open Outlook Data File, and choose the PST. It appears as a separate tree in the folder pane.
Drag folders (Inbox, Sent Items, your own folders) from the PST onto the new IMAP account. Outlook uploads them to the server over IMAP.
Wait. Outlook uploads in the background; a large mailbox can take hours. Keep the computer awake and online.
Check the result in webmail at https://mail.zomail.io: folder counts should match.

Tips from experience:

Drag one large folder at a time rather than the whole tree. If something stalls, you know where.
If Outlook reports items it could not copy, look for unusually large messages and handle them separately.
Do the bulk upload before cutover, then a second, smaller drag of anything that arrived after the export.

Step 4: Calendars and contacts

IMAP carries mail only, and classic Outlook for Windows does not sync calendars over CalDAV. So:

Data	Route out of Microsoft 365	Into the new system
Mail	PST export	Drag into the IMAP account in Outlook
Calendar	Export to an .ics file	Import through a CalDAV app such as Apple Calendar or Thunderbird
Contacts	Export to CSV or vCard	Import through a CardDAV app
Files	Download from OneDrive / SharePoint	Upload to the new Drive
Rules	Note them down	Recreate as server-side filters

Be clear with your team about one change: if they live in Outlook today, their Zomail calendar will be in the webmail, the Zomail mobile app and phone calendars (via CalDAV), not inside Outlook for Windows. Zomail does not offer Exchange ActiveSync.

Step 5: Switch DNS and leave the tenant cleanly

When the bulk of mail is copied, change DNS at your registrar or DNS host:

MX: replace the Microsoft record (*.mail.protection.outlook.com) with mx.zomail.io. See MX records explained.
SPF: replace include:spf.protection.outlook.com with include:_spf.zomail.io, unless other services still send through Microsoft. How to set up an SPF record explains the details.
DKIM: remove Microsoft's selector1/selector2 CNAMEs and add Zomail's zm1/zm2 CNAMEs.
Autodiscover: remove or replace the autodiscover CNAME that points to Microsoft. If you leave it, Outlook keeps trying to connect to Microsoft 365 when people add accounts.

Two tenant gotchas catch people out:

Internal mail stays inside Microsoft 365 while the domain is still an accepted domain in the tenant. A colleague who still has an Exchange mailbox will send to anna@example.com and Microsoft will deliver it internally, ignoring your new MX. Cut everyone over together, then remove the domain from the tenant.
Removing the domain requires first removing it from every user, group and alias in the tenant. Leave time for this.

After cutover, do a final PST top-up for each user, reconnect phones with the Zomail app or any IMAP app (see phones and mobile), and only then cancel licences.

What you gain and what changes

Leaving Microsoft 365 is a trade-off, and it is worth being honest about it. Microsoft offers a deep Office desktop suite, Teams and tight Outlook/Exchange integration. If those are central to your work, our Microsoft 365 alternatives article helps you weigh the options.

If your needs are mainly email on your own domain, a calendar, files and browser-based Office documents, a simpler suite can be enough. Zomail includes those, plus a guided DNS page and a bulk importer for other sources; it is priced per mailbox per month, with current prices on the pricing page, and our migration guide walks through the details.

FAQ

Why does my Microsoft 365 password not work in an email importer?

Microsoft has disabled basic authentication (username and password) for IMAP in Exchange Online. Importers must use OAuth instead. Zomail's importer does not support Microsoft OAuth yet, so use the PST export and Outlook drag route.

Can I import a PST file directly into Zomail?

Not through the Zomail interface today. Open the PST in classic Outlook, add your Zomail mailbox over IMAP, and drag folders across; Outlook uploads them to the server.

Will my Outlook calendar sync with the new mailbox?

Not inside Outlook for Windows, which syncs mail over IMAP but has no built-in CalDAV. Export your calendar to .ics and import it into the new calendar through a CalDAV app, then use the webmail, the Zomail app or your phone's calendar.

How long should I keep my Microsoft 365 licences?

Until every mailbox has been copied, checked in webmail and topped up after the DNS switch. A week or two of overlap is common. Microsoft keeps data only for a limited time after cancellation, so export first.

Does Outlook still work after migrating from Microsoft 365?

Yes, for email. Outlook connects to the new mailbox over IMAP and SMTP with an app password. Calendar, contacts and shared mailboxes are then used through webmail, the mobile app or CalDAV/CardDAV apps.