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What Is My Office 365 Hostname? Simple Guide & Tips

Posted on by William Zheng

Ever tried to set up email on a new device or connect an app, only to get stuck wondering, “What is my Office 365 hostname?” You’re not alone! Many people face this question when syncing accounts or troubleshooting connectivity issues.

Knowing your Office 365 hostname is key to smooth setup and secure access. In this article, we’ll explain exactly what it is, why you need it, and walk you through simple steps to find it fast.

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What is My Office 365 Hostname? A Complete Guide

Trying to find your Office 365 hostname for mail setup, troubleshooting, or network configurations? You’re not alone! Locating the correct hostname is essential if you want to set up mail clients (like Outlook, Thunderbird, or your phone’s mail app), integrate with other systems, or work with your IT department. In this article, I’ll break down what a hostname is, why you need it, how to find yours quickly, and the best practices to avoid confusion.

Understanding the Office 365 Hostname

First, let’s get clear on what a “hostname” means in the context of Office 365.

  • Hostname: This is the address or label assigned to a server within a network so that you (and other computers) can easily locate or connect to it.
  • In Office 365: The hostname usually refers to the address of your email server (used for connecting by mail apps), your tenant domain for services, or sometimes a specific service endpoint like Exchange Online.

Why It’s Important:
When configuring email clients, syncing devices, or connecting third-party tools, you’ll often need to input the correct Office 365 hostname. If you use the wrong one, you’re likely to run into connection issues.

Common Hostnames Used in Office 365


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Depending on what you are trying to do, you may need different kinds of hostnames. Here are the most common ones:

  1. Exchange Online (Email Service) Hostname
  2. Used for setting up email clients via IMAP, SMTP, or Exchange.
  3. Tenant Hostname
  4. The unique domain assigned to your Office 365 tenant, useful for admin and some integrations.
  5. Autodiscover Service Hostname
  6. Helps clients automatically find your mail server settings.
  7. Other Service Hostnames
  8. SharePoint, Teams, or OneDrive may have their own relevant hostnames.

In most cases, if you’re looking to set up your email client, you’ll need the Exchange Online server hostname.

How to Find Your Office 365 Hostname: Step-by-Step

Let’s walk through the ways you can quickly locate your Office 365 hostname.


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1. For Outlook and Email Clients

Most users want the email (Exchange Online) server hostname. Here’s how you find it:

For Automatic Configuration (Recommended)

If you use Outlook or a mail app that supports “autodiscover,” you likely don’t need to enter the hostname manually—just enter your email and password. The app finds the right settings for you.

Manual Setup – IMAP/SMTP

If your client requires manual entry, use these default hostnames:

  • IMAP server: outlook.office365.com
  • SMTP server: smtp.office365.com

Unless your organization uses custom settings, these server addresses work for most Office 365 mailboxes.

Finding the Hostname Via Outlook or Office 365 Web:

  1. Log in to your Office 365 account via web browser.
  2. Go to Outlook.
  3. Click the Settings gear icon (top right), then View all Outlook settings.
  4. Navigate to Mail > Sync Email.
  5. Here, you may see your server address listed, especially if you’re accessing “POP and IMAP settings.”


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  • Tip: IMAP and SMTP addresses are generally the same for all Office 365 accounts unless your organization has a custom setup.*

2. For Admins: Finding Your Tenant Hostname

If you’re an administrator looking for the tenant’s unique Office 365 hostname for directory integrations or settings:

  1. Go to the Microsoft 365 Admin Center.
  2. Under Settings, select Domains.

  3. You’ll see a list of your verified domains, including your default domain (often looks like yourcompany.onmicrosoft.com).

  4. This default domain is your tenant hostname.

  5. Example:*
    If your primary domain is contoso.com, your tenant hostname might be contoso.onmicrosoft.com.

3. Using PowerShell

For advanced users, Microsoft 365 can be queried via PowerShell.

  • Open PowerShell.
  • Connect to Exchange Online with your admin credentials:
    Connect-ExchangeOnline -UserPrincipalName [email protected]
  • To find mailbox server details:
    Get-Mailbox | Format-List PrimarySmtpAddress,ServerName

Note: For most cloud-based Office 365 accounts, this will confirm outlook.office365.com as the hostname.

Practical Tips and Best Practices

Want to avoid common pitfalls? Here’s what you should keep in mind:

Know Which Hostname You Actually Need

  • For 95% of users configuring mail apps, you’ll want outlook.office365.com (IMAP/SMTP).
  • For domain or tenant-level configurations, look for yourcompany.onmicrosoft.com.

Always Use Secure Ports

  • IMAP (for receiving): Port 993 with SSL/TLS
  • SMTP (for sending): Port 587 with STARTTLS or SSL/TLS

Use Autodiscover When Possible

  • Most modern clients support “autodiscover”—let them do the work for you to reduce setup errors.

Don’t Share Admin Hostnames Publicly

  • Admin and tenant hostnames can reveal information about your organization. Only share them with verified team members or support personnel.

Document Your Settings Internally

  • Keep an internal wiki or document where your team’s Office 365 hostnames and email server settings are listed for quick access.

Common Challenges and How to Overcome Them

It’s normal to run into hurdles when dealing with hostnames. Let’s tackle a few you might see:

  • Challenge: “My email client says it can’t connect to the server.”
  • Solution: Double-check you’re using outlook.office365.com, the correct ports, and SSL/TLS is enabled. Ensure your login credentials are correct.
  • Challenge: “I see different hostnames or server addresses provided by IT.”
  • Solution: Large organizations may use custom domains or routing. Check with your IT department or admin if unsure.
  • Challenge: “I’m setting up a custom integration or migration and need my tenant hostname.”
  • Solution: Always use the yourcompany.onmicrosoft.com format unless otherwise instructed by an admin guide.
  • Challenge: “What if I have a hybrid environment?”
  • Solution: Hybrid setups may require different on-premises hostnames—coordinate with IT or consult proper documentation.

Cost Tips Related to Office 365 Setup

While finding your hostname is free, setting up or troubleshooting Office 365 mail and services efficiently can reduce costs in several ways:

  • Avoid engaging paid technical support by using built-in autodiscover and documented steps.
  • Minimize time spent onboarding new users by keeping clear hostname setup guides.

  • Prevent downtime, which can be costly for your business, by ensuring quick and accurate mail configuration.

  • Pro tip:* Shipping costs don’t apply directly here, but time spent troubleshooting ambiguous server names can “cost” your business in productivity. Have your hostname documentation up-to-date to ship new devices and set up users faster.

Conclusion

Finding your Office 365 hostname doesn’t have to be complicated! For most users, simply use outlook.office365.com for mail setup. For tenant and service integrations, identify your company’s default domain (yourcompany.onmicrosoft.com). When in doubt, default to autodiscover, check your mail settings, or ask your IT team. By following the best practices above, you can configure your email and Office 365 services quickly and securely.

Frequently Asked Questions (FAQs)

1. What is the default Office 365 email server hostname for IMAP and SMTP?
The default IMAP hostname is outlook.office365.com (port 993 with SSL/TLS), and the SMTP hostname is smtp.office365.com (port 587 with STARTTLS). These work for most Office 365 accounts unless your organization uses custom servers.

2. How can I find my Office 365 tenant’s hostname?
Go to your Microsoft 365 Admin Center, choose “Domains,” and look for your default domain, usually in the format yourcompany.onmicrosoft.com. This is your tenant hostname.

3. Do I need to enter hostnames manually when setting up Outlook or mobile email apps?
Generally, no. Modern clients support “autodiscover” and can configure settings automatically when you enter your email and password. Only enter hostnames manually if prompted or if autodiscover fails.

4. What should I do if my email client can’t connect using the recommended hostnames?
Double-check your server addresses and ports, ensure SSL/TLS is enabled, and verify your login. If issues continue, contact your IT administrator—your organization may use custom configurations.

5. Is there any cost involved in finding or using my Office 365 hostname?
No, it’s free to look up and use your Office 365 hostname. However, accurate documentation and using autodiscover can save you time, prevent productivity loss, and help keep support costs down.

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