If you are experiencing this error, it means that your email traffic is being denied by Outlook's servers due to a low reputation IP address. Even if you are a paying customer, this can still occur if you are using a Microsoft 365 trial tenant. However, there is a way to fix this issue by reaching out to Microsoft support.
To fix the "550 5.7.708 Access denied" error, follow these steps:
Step 1: Contact Microsoft Support
The first step is to contact Microsoft support to request an exception for your low reputation IP address. This will allow you to use Outlook without any issues until you are ready to purchase a license. To contact Microsoft support, follow these steps:
Open Outlook and click on the "File" tab in the top left corner.
Click on "Help" and then select "Contact Support."
Choose the type of support you need, such as technical support or billing support.
Follow the prompts to connect with a Microsoft support representative.
Step 2: Explain the Issue
Once you have reached out to Microsoft support, explain the issue you are facing and provide them with any necessary details. This will help them to understand the nature of the problem and provide you with a solution.
Step 3: Request an Exception for Your IP Address
After explaining the issue to the support representative, request an exception for your low reputation IP address. This will allow you to use Outlook without any further issues until you are ready to purchase a license.
In conclusion, the "550 5.7.708 Access denied" error can be frustrating for Outlook users, but it can be fixed by contacting Microsoft support and requesting an exception for your low reputation IP address. By following the steps outlined above, you can quickly resolve this issue and continue using Outlook without any further interruptions.
you can also check out this link for further troubleshooting: https://learn.microsoft.com/en-us/exchange/troubleshoot/email-delivery/ndr/fix-error-code-5-7-700-through-5-7-750.
