Resolve "hostname is not valid" error for Microsoft tenant domain

Introduction

This article explains how to resolve the "hostname: example.onmicrosoft.com is not valid" error when creating a new Microsoft Tenant Domain. Understanding the cause of this error and the steps to resolve it will help you successfully create Tenant Domains.

In this article:

• Understanding the error
• Why this error occurs
• How to verify domain availability
• How to resolve the error

Understanding the error

If you encounter the "hostname: example.onmicrosoft.com is not valid" error while creating a new Tenant Domain, it indicates that the Domain name you're trying to use is unavailable.

Why this error occurs

This error appears for one of two reasons:

1. Domain already exists: The Domain is already taken and exists in the Microsoft ecosystem, being used by another Microsoft Organization.

2. Previous creation attempt: The Domain was previously attempted to be created in the Platform and either did not succeed or has not been removed from the system yet.

How to verify domain availability

You can verify if a Tenant Domain is already in use by another Microsoft Organization using the Microsoft Tenant Availability Check Tool:

URL: https://o365.rocks/

Enter the Domain name you want to use to check its availability in the Microsoft ecosystem.

How to resolve the error

To resolve this issue, you have two options:

Option 1: Use a different domain name

Choose a different Domain name that is not already in use and create your Tenant Domain with the new name.

Option 2: Remove the domain from the platform

If the Domain is available in your Platform grid and meets the deletion criteria, you can remove it and reuse the name:

1. Locate the Domain in your Tenant Domains list.
2. Click the Delete button next to the Domain.
3. After deletion, retry creating the Tenant Domain with the same name.

Deletion criteria:

Only Tenant Domains that meet the following conditions can be removed:

• Domain Status is 'Invalid' (creation was not successful), OR
• The Domain has no Subscriptions associated with it

Domains in other states (e.g., 'New', 'Suspended') cannot be deleted from the Platform.

Summary

The "hostname is not valid" error occurs when attempting to create a Tenant Domain that either already exists in the Microsoft ecosystem or was previously attempted in the Platform without successful completion. Verify Domain availability using the Microsoft Tenant Availability Check Tool at https://o365.rocks/. Resolve the error by choosing a different Domain name or by deleting the existing Domain from the Platform grid using the Delete button if it has 'Invalid' Status or no associated Subscriptions. Domains in other states such as 'New' or 'Suspended' cannot be deleted.