Moving business email from a web host or ISP to Microsoft 365

Why email on a web host becomes a problem

Many small businesses started with email bundled with their website hosting or internet connection. It was cheap and it worked. Over time the limits show: small mailbox sizes, weak spam filtering, no multi-factor sign-in, no shared calendars and no proper way to hand a mailbox over when someone leaves. Some hosts quietly retire their email service, and ISP-provided addresses tie you to that provider.

Moving to Microsoft 365 puts mail, calendar, files and sign-in security in one place under your control. The move itself is straightforward for most small offices, but there are a few traps around how mail was stored and how the domain is managed. A little preparation avoids the classic outcome of someone discovering on Monday that ten years of email is missing.

Find out where mail actually lives

With IMAP, email is stored on the host's server and every device sees the same folders. That is the easy case: a migration tool can log in and copy everything. With POP, mail was usually downloaded to one computer and deleted from the server, so the only copy of years of history is in an Outlook data file on someone's PC. A migration from the server would bring across almost nothing.

Check each person's setup before planning. Look at Outlook's account settings on each computer and ask staff whether they read mail on several devices. Find any old PST data files, including ones on former employees' computers. Those can be imported into Microsoft 365 mailboxes, either by Outlook or through Microsoft's import service for larger volumes.

Domain and DNS: know who controls them

To use your domain with Microsoft 365 you need access to its DNS settings, which may be with your domain registrar, your web host or a separate provider such as Cloudflare. Find the login before you start. Microsoft gives you a verification record to prove you own the domain, then the records needed for mail: MX, SPF, autodiscover and DKIM.

Be careful not to break the website. If the web host also manages DNS, only change the mail-related records and leave the website records alone. Note down every existing record before making changes so you can put anything back if needed. Lower the time-to-live on the MX record a day before cutover so the switch takes effect quickly.

Copying the mail across

For IMAP mailboxes, Microsoft 365's migration feature can copy mail from the old server using each user's credentials, or a third-party tool can do it with better reporting. Run the bulk copy before cutover while staff keep working. IMAP migration copies email only, so export calendars and contacts from the old system and import them separately.

For POP users with an Outlook data file, add the new Microsoft 365 account to Outlook after cutover and either import the PST or drag folders across. Large files take time and should be done over a fast connection. Keep the original PST files in a safe place until everyone confirms their history is complete, then retire them rather than leaving copies on random computers.

Cutover day

Change the MX record to Microsoft's address at a quiet time, then run a final copy from the old server to catch anything that arrived in between. Set up Outlook on desktops, the Outlook app on phones, and remove the old account from each device so people do not keep sending from the old server by habit.

Expect a few loose ends. Website contact forms, scanners, printers and accounting software that send email through the old host's mail server need reconfiguring. Forwarding rules and aliases set up years ago need recreating as shared mailboxes or aliases in Microsoft 365. Make a list of every address the business uses, including info and accounts, before the switch.

After the move

Turn on multi-factor sign-in for every mailbox straight away; the old host probably had nothing comparable. Set up SPF, DKIM and DMARC so other providers accept your mail and your domain is harder to spoof. Check that new mail is arriving, that replies are not going to junk at a few test recipients, and that shared mailboxes work.

Keep the old hosting mailboxes for a few weeks in case something turns up, then close them so they cannot be broken into and used to send spam. Review your web hosting plan too, because removing email from it may let you move to a cheaper plan. Finally, add a Microsoft 365 backup now that mail lives in the cloud.