Exchange Online 550 5.7.708 — Outbound email blocked on new Microsoft 365 trial tenant

Question

Service and environment

Service: Microsoft Exchange Online

Subscription: Microsoft 365 Business Standard (no Teams)

Subscription status: Active free trial

Tenant: Newly created Microsoft 365 business tenant

Region: Australia

Licensing: Exchange Online (Plan 1) assigned and enabled

Domain: Custom business domain added to Microsoft 365

Problem description

I recently established a new Microsoft 365 tenant for an Australian business and configured Exchange Online using Microsoft 365 Business Standard.

Although the mailbox is accessible and an Exchange Online licence is assigned, outbound emails to external recipients are being rejected.

The non-delivery report contains the following error:

550 5.7.708 — Service unavailable. Access denied, traffic not accepted from this IP. AS(8562)

The failed message was generated on 23 October 2026 at 04:14:54 UTC.

The recipient was an external Gmail address.

Steps to reproduce

Sign in to Outlook using the licensed Exchange Online account.

Compose a new email to an external Gmail address.

Send the message.

Receive a non-delivery report containing error 550 5.7.708.

Expected result

Exchange Online should successfully deliver legitimate outbound business correspondence to external recipients.

Actual result

The message is rejected with error 550 5.7.708 before successful delivery.

Troubleshooting performed

I have:

Confirmed that the Microsoft 365 Business Standard subscription is active.

Confirmed that Exchange Online (Plan 1) is enabled for the affected user.

Verified that the account has an Exchange Online licence assigned.

Reviewed Microsoft's documentation concerning outbound IP reputation restrictions affecting trial tenants.

Attempted to access technical support through Microsoft 365 Admin Centre → Support → Help & support.

Attempted to use the Australian telephone support number displayed in the Admin Centre, but the number does not connect.

Checked the Service Request History page; no option to create a new written support request is displayed.

Microsoft's documentation suggests that newly established trial tenants may encounter this restriction and require Microsoft Support to arrange an IP address exception.

Question

What is the supported procedure for requesting an Exchange Online outbound IP reputation exception for error 550 5.7.708 when the Microsoft 365 Admin Centre only provides a telephone support number that cannot be reached?

I would appreciate guidance on an official written support or escalation channel through which this restriction can be investigated and resolved.

Thank you.

Answer 1

Hi @Jai

You're receiving the 550 5.7.708 Service unavailable. Access denied, traffic not accepted from this IP error because Microsoft's outbound mail protection has identified the sending IP address as having a low reputation.

According to NDR error codes 550 5.7.703, 550 5.7.705, 550 5.7.708, and 550 5.7.750 - Microsoft Support, this issue is more likely to affect newly created or trial tenants.

Since your tenant is on a trial subscription, it is recommended contacting Microsoft Support to request an IP address exception. This type of restriction cannot be removed through tenant-side configuration alone. To proceed, please open a support request through the Microsoft 365 Admin Center and provide the complete NDR details, affected sender address, and tenant information.

-Sign in to the Microsoft 365 Admin Center

-Click Help & Support

-If Support Assistant opens, toggle/turn off the Support Assistant option.

-In the search box, type Support and click →.

-Look for and select Contact support.

-You should then be given the option to choose your preferred contact method, such as Email or Phone.

For further instructions, you can follow this guide: Get support - Microsoft 365 admin | Microsoft Learn. 

I hope this information is helpful.