How to Migrate Email Between Providers Without Losing Mail

Changing email provider scares many business owners, because email is the one service nobody can afford to lose. The risk is manageable. If you do things in the right order, customers will not notice anything, and no message will go missing. The principle is simple: build the new mailboxes first, copy the old mail across, and only then redirect new mail.

Plan the move

Before touching anything, take stock:

• List every mailbox, alias and forwarder on the old system.
• Note the size of each mailbox. This decides how long the copy takes.
• Find out where DNS is managed, and who has access to it.
• Check which devices and applications use the mailboxes: phones, laptops, website forms, scanners, accounting software.
• Find out if any non-mail services depend on the old provider, such as shared calendars.

Choose a quiet time, such as a weekend, for the DNS switch.

The migration steps

Step 1: create the new mailboxes

Set up every account on the new service with the same addresses. Create aliases and forwarders too. You need each user's old password only if you will use a password-based copy tool. Otherwise, new passwords are fine, but make sure everyone is told.

Step 2: lower the TTL

A day or two before the switch, reduce the TTL on your MX records to a short value such as 300 seconds. The old, long TTL may be cached by other servers, which delays the change. A short TTL means senders learn about the new servers quickly.

Step 3: copy the existing mail

The standard method is an IMAP sync. A migration tool logs into both the old and new mailboxes and copies folders and messages from one to the other, keeping the folder structure and read flags. There are several well-known open-source and commercial tools for this, and many hosting providers offer to run it for you. For each mailbox, the tool needs the old server name, old credentials, the new server name and new credentials.

Run a first full sync a few days before the switch. It can take a long time for large mailboxes, and it is safe to repeat because the tool only copies what is missing.

Step 4: switch the MX records

1. At the agreed time, replace the old MX records with the new provider's.
2. Update SPF to authorise the new servers and remove the old ones.
3. Publish the new DKIM key, and check the DMARC record.
4. Send test messages to and from each mailbox.

For a short time, some senders will still deliver to the old servers because of caching. That is expected.

Step 5: run a final sync

After the switch, run the IMAP sync once more. It picks up any messages that arrived at the old server during the changeover. Repeat a day later, and keep the old mailboxes alive for at least a week or two.

Step 6: reconnect devices

Update server names on phones and computers, or remove the old account and add the new one. Tell staff the new webmail address if it has changed. Check anything that sends mail automatically: website forms, printers and scanners, accounting and shop software. These often use the old SMTP server and will quietly stop working.

Timeline example

When	Action
One week before	Create mailboxes, run first sync
Two days before	Lower TTL on MX records
Switch day	Change MX, SPF, DKIM, test
Day after	Final sync, reconnect devices
Two weeks later	Check old system is empty of new mail, then close it

Traps to avoid

• Cancelling the old plan before the final sync, which can delete the only copy of recent mail.
• Forgetting aliases and forwarders, so some addresses silently stop working.
• Leaving old MX records in place alongside the new ones.
• Skipping SPF and DKIM updates, which sends the first messages from the new host to spam.
• Not telling users, who then keep sending from the old server settings.

Check afterwards

Confirm that mailbox sizes on the new system roughly match the old ones, that the folder structure looks right, and that search works. Ask a few users to spot-check old messages. Keep a backup of the old mailboxes, or export them, before you finally close the account.

When the old provider will not cooperate

Sometimes the old host is slow to give details, or the account owner has left the company. In that case, work out who controls the domain registration first, because that is where the final authority lies. If you cannot get server details, mailbox owners can still export their mail from a desktop client and import it into the new mailboxes. It is slower, but it works without help from the old provider. Document everything you do so that the next person can follow the same steps.

Free email migration with Zebra Hosting

Zebra Hosting's team moves your site, databases and email for free, and mailboxes on email plans are set up automatically within minutes of payment, so the new side is ready quickly. Support is available in 17 languages. Read how it works on the migration page or choose a plan from the email hosting options.