Mail Stays on the Old Host After Switching Email Providers: The Fix

The pattern is unmistakable: you changed the MX records, mail from Gmail and customers arrives at the new provider, but messages from your own website, from someone still using the old webmail, or from a colleague on the old host vanish or bounce with "user unknown". The old server never looks up MX for a domain it believes it hosts. It delivers locally, into mailboxes nobody reads any more. One setting on the old host fixes it, and the setting has a different name on every panel.

Quick answer

On the old host, tell it that your domain's mail is handled elsewhere. In cPanel that is Email Routing set to Remote Mail Exchanger; in Plesk it is turning off the mail service for the domain; in Google Workspace and Microsoft 365 it is removing the domain or changing it to an external relay. Then point your website's contact form at mail.oqumail.com on port 587, so site mail leaves through a real SMTP login instead of the local mailer.

How to recognise it

• Mail from outside (Gmail, customers) arrives at the new provider. Mail from your website, your old webmail, or a colleague who still uses the old host does not.
• The bounce, if there is one, comes from the old host's server name and says "User unknown" or "No Such User Here" even though the address exists on the new provider.
• Postfix logs on a server you run show "mail for yourdomain.com loops back to myself", which means MX points at a server that is not configured to accept the domain.
• The MX lookup shows the new provider correctly, which is why DNS changes do not help.

Fix it on the old host

• cPanel (most shared hosts): Email, Email Routing, pick the domain, choose Remote Mail Exchanger, Change. Then delete the old mailboxes under Email Accounts once you have copied anything you need.
• Plesk: Mail, the domain, Mail Settings, untick "Activate mail service on this domain" (or set it to disabled), OK.
• DirectAdmin: E-mail Accounts, the domain, Local Mail Server setting; set the domain to use remote mail exchange.
• Google Workspace: Admin console, Domains, Manage domains. Remove the domain, or if you must keep it for another service, set up a routing rule that sends unknown recipients to the new MX.
• Microsoft 365: Admin center, Domains. Remove the domain, or in Exchange admin change the accepted domain from Authoritative to Internal relay so unknown users are delivered externally.
• Your own Postfix: remove the domain from mydestination and virtual_mailbox_domains (or add it to relay_domains with a transport to the new MX).

Fix the website separately

Contact forms and shop notifications on the old host usually call the local mailer, which skips DNS. Even with routing fixed, that mail leaves from an IP that is not in your SPF record and lands in spam. Install an SMTP plugin and send through a mailbox on the new provider: WordPress users can follow the WordPress SMTP guide; other sites set host mail.oqumail.com, port 587, STARTTLS, and the mailbox login.

Then confirm

1. Send a test from the old webmail (if it still exists) to your address. It should now arrive at the new provider.
2. Submit your own contact form and check the message arrives, and that Show original in Gmail reports SPF (Sender Policy Framework — a list of servers allowed to send email as your domain)=pass for the domain.
3. Ask any colleague still on the old host to send one message, then move their mail app to the new provider; the migration guide covers the order.

Common questions

Can I keep some mailboxes on the old host?

Not for the same domain. A domain's MX points at one provider, and the old host either handles every address locally or none. Move every address, or put the second provider on a subdomain.

Why does Gmail mail arrive but my own does not?

Gmail asks DNS where to deliver and follows the MX. The old host skips that question for a domain it hosts and delivers to itself. Nothing is wrong with DNS; the old host is just not asking.

I cancelled the old hosting. Is that enough?

Yes, once the account is actually deleted. A suspended-but-present account can keep accepting mail for the domain for weeks.

Want to see how your own domain is set up? Use the free SPF checker and MX lookup: they run in your browser and store nothing.