Fix Inbound Email Failing for IONOS Domain on Microsoft 365
Question details
Users can successfully send emails but are unable to receive incoming messages after moving an IONOS-hosted domain to Microsoft 365.
- Product
- Microsoft 365 / IONOS
- Device & OS
- not provided
- Scenario
- Migrating email services to Microsoft 365 while keeping the domain's DNS management at IONOS.
- Observed behavior
- Outbound emails are sent without issue, but inbound emails fail to deliver due to incorrect or missing MX records in the DNS settings.
Ensure you have administrator access to both your Microsoft 365 Admin Center and your IONOS control panel before making any DNS modifications.
Update MX and DNS Records in IONOS for Microsoft 365
Correcting the MX record in your IONOS DNS settings ensures that incoming emails are accurately routed to your new Microsoft 365 inbox.
When a domain is moved to Microsoft 365 but the DNS remains managed by IONOS, the MX (Mail Exchanger) record must be explicitly updated to point to Microsoft's Exchange Online servers. Without this crucial step, other servers cannot locate your new inbox, resulting in incoming mail failures while outbound mail continues to function normally.
Log in to the Microsoft 365 Admin Center, navigate to 'Settings', and select 'Domains'. Click on your domain to find your exact Exchange Online MX record value.
Log in to your IONOS account, go to the 'Domains & SSL' section, and click the gear icon next to your domain to access its DNS settings.
Locate the existing MX record and update it to the destination value provided by Microsoft (usually resembling 'yourdomain-com.mail.protection.outlook.com').
Delete any conflicting or legacy MX records that are still pointing to the old IONOS mail servers to prevent routing conflicts.
Ensure you also add or update the SPF (TXT) and Autodiscover (CNAME) records as specified in the Microsoft 365 Admin Center, then save your changes.
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Frequently Asked Questions
Why can I send emails but not receive them after migrating to Microsoft 365?
This scenario typically occurs when your domain's MX (Mail Exchanger) records are missing or still pointing to your previous email provider. MX records specifically instruct the internet on where to route incoming emails.
How long does it take for inbound emails to work after updating the MX record in IONOS?
DNS modifications, including MX record updates, can take up to 72 hours to fully propagate across the internet globally. However, it is common to start receiving emails within a few hours.
Do I need to update other DNS records besides the MX record for Microsoft 365?
Yes, for optimal email functionality and deliverability, you should also update your SPF (TXT) record to prevent your outbound emails from being flagged as spam, and set up the Autodiscover (CNAME) record to help mail clients connect automatically.
