Set up the MX record at IONOS

The MX hosts of IONOS

For mailboxes at IONOS the MX records point to mx00.ionos.de and mx01.ionos.de. IONOS sets them automatically with its own name servers; if the name servers are elsewhere, they must be created there.

10 mx00.ionos.de
20 mx01.ionos.de

Switching to Microsoft 365 or Google Workspace

Microsoft 365 expects exactly one MX pointing to your-domain-com.mail.protection.outlook.com (the admin center shows the exact value), Google Workspace one MX pointing to smtp.google.com with priority 1. Remove the old IONOS MX records, otherwise mail keeps arriving at IONOS depending on priority. Lower the TTL before the switch and create the mailboxes at the new provider first so no mail is rejected.

How to add the MX record at IONOS

The way to the IONOS DNS editor:

• Sign in to the IONOS account and open "Domains & SSL".
• Click the gear icon next to the domain and choose "DNS".
• Choose "Add record", pick the type (TXT, MX, CNAME) and host name, paste the value, save.
• Type MX, host name @ (apex domain), value: the host name of the mail server without a trailing dot, plus the priority. For several mail servers create one entry each with its own priority and remove old MX entries.
• Changes usually apply within minutes; the default TTL is one hour.
• Use "@" as the host name for the apex domain; IONOS shows it as the domain name.

Typical mistakes at IONOS

• Trailing dot or missing priority: some editors require both, others reject them.
• Old MX records not removed after the switch.
• MX pointing to an IP address or a CNAME instead of an A record.
• Mailboxes not yet created at the new provider, mail is rejected.

Verify and keep an eye on it

After saving, the change at IONOS usually applies within minutes. The checker below queries the authoritative name servers and shows right away whether the MX record is read correctly. DomainWarn keeps checking the record afterwards and alerts you when it changes or disappears, for example after a migration or one click too many in the DNS editor.

Frequently asked questions

Can I keep mailboxes at IONOS and use Microsoft 365 only for sending?

Receiving and sending are separate: MX records decide receiving, SPF and DKIM decide sending. Both can be mixed, but a clean switch is usually simpler.

Which priority is right?

The lowest number wins. With one mail server 10, with several 10 and 20. The value only has relative meaning.