How to resolve the issue of prolonged loading times for organizational structures in Outlook or Teams?

Question

Within the office network, we have observed that when viewing an individual's organizational structure in Teams or Outlook, random instances of slow loading or failure to load may occur.

We would like to know the resource URLs used when loading organizational structures in Teams and Outlook.

This information will enable us to optimize traffic specifically for these URLs.

Answer 1

Hi @Li, Jason

Thank you for posting your question in the Microsoft Q&A forum.    

I understand how intermittent slow loading or failures when viewing the organizational structure in Teams or Outlook can be frustrating, especially within an office network environment. 

Since this issue appears to have been affecting multiple users over a longer period within your tenant, it would require investigation at the tenant or service level. As a forum moderator, I’m only able to assist with general guidance and basic troubleshooting, and don’t have access to your tenant configuration or service diagnostics. For further investigation, submitting a support ticket would be the appropriate next step so the support team can review this in more detail. 

A technical support engineer can perform a remote session to investigate the situation, verify the backend configurations, and run any necessary synchronization tools to resolve the problem. If the issue requires further attention, they can escalate it to a specialized team for deeper analysis.       

Here’s what your Microsoft 365 Global Admin (IT Admin) should do next:      

• Submit a Service Request: The Global Admin should create a service request with Microsoft support to get advanced technical assistance and diagnostics. For detailed instructions on how to get support, please refer to Get support - Microsoft 365 admin.        
• Find Your Microsoft 365 Admin: If you’re unsure who the Global Admin is within your organization, you can find guidance on locating them here: How do I find my Microsoft 365 admin? - Microsoft Support.    
• If your subscription is managed through a Microsoft partner or reseller, they can also assist with opening a support request and liaising with Microsoft on your behalf.     

Note: If you’re an end-user, please coordinate with your Office 365 Global Administrator to handle these steps.    

I apologize for redirecting you the related team support, as the moderators in this community don’t have access to the detailed system needed to troubleshoot this effectively due to privacy and security constraints. But Microsoft’s support team has elevated permissions and access to backend systems that we, as community moderators, do not. This ensures your issue is handled with the right tools and expertise and helps you get a faster resolution.      

Hopefully they will be able to help with your issue and if you have any other questions or need further assistance, feel free to ask.   

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Answer 2

The specific resource URLs or endpoints used by Outlook and Teams to load organizational structures are not listed.

However, the behavior described (intermittent slow loading or failure to load organizational data inside the corporate network) aligns with general Microsoft 365 performance and network issues, which can be investigated and optimized as follows:

1. Measure latency and round-trip time (RTT)
   • Use ping or PsPing to measure RTT to Microsoft 365 endpoints such as outlook.office365.com or relevant SharePoint/Exchange URLs, for example:
     • psping -4 outlook.office365.com:443
     • psping -4 -n 20 yourSite-my.sharepoint.com:443
   • High or inconsistent RTT indicates broader network issues that will also affect organizational structure loading.
2. Check DNS performance and geolocation
   • Capture a network trace (Netmon or Wireshark) while reproducing the slow org-structure load.
   • Filter for DNS:
     • Netmon: dns
     • Wireshark: dns or dns.time
   • In Wireshark, add the DNS time as a column by right‑clicking the [Time: x.xxxxxx seconds] field under Domain Name System (response) and selecting Apply as Column, then sort by that column to find slow DNS responses.
   • If DNS responses are slow, test directly with psping <DNS-IP>:53. Persistent latency here points to DNS or broader network issues, not the application.
   • A ping to outlook.office365.com will show which datacenter is being used (for example, outlook-namnorthwest.office365.com), which helps verify that DNS geolocation is sending traffic to an appropriate region.
3. Analyze latency between client, proxy/egress, and Microsoft 365
   • In Netmon or Wireshark, filter by client and Microsoft 365/proxy IPs to examine RTT:
     • Netmon example: .Protocol.IPv4.Address == <clientIP> AND .Protocol.IPv4.Address == <egress-or-M365-IP>
     • Wireshark example: ip.addr == <clientIP> && ip.addr == <egress-or-M365-IP>
   • Use the Time Offset or Time Delta columns to identify long gaps between request and response, especially in TLS Application Data packets. Long gaps during page refreshes correlate with perceived slowness in Outlook/Teams UI.
4. Verify TCP settings (window scaling, SACK, MSS)
   • Capture a trace and filter for SYN packets:
     • tcp.flags.syn == 1
   • For each connection of interest, inspect the SYN/SYN‑ACK:
     • Confirm TCP Window Scaling is present and appropriate; lack of scaling on legacy devices can cause throughput bottlenecks.
     • Confirm Selective Acknowledgment (SACK) is permitted in both SYN and SYN/ACK. If disabled, retransmissions become inefficient and can cause performance degradation.
     • Check TCP Max Segment Size (MSS) to ensure packets can carry the maximum amount of data possible.
5. Check idle timeouts and long‑lived connections
   • Outlook on the web and related Microsoft 365 experiences use long‑term connections. If perimeter devices (proxies/firewalls) terminate idle TCP sessions (commonly at 100–300 seconds), clients may repeatedly try to reuse dead connections, causing hangs and slow loads.
   • Work with the network team to ensure idle timeout settings on proxies/firewalls are compatible with long‑lived Microsoft 365 connections.
6. Investigate proxy authentication and scalability
   • If traffic to Microsoft 365 goes through a proxy:
     • In Netmon, add NTLMSSP Summary and Time Delta columns and filter for .property.NTLMSSPSummary to see how long proxy authentication takes per new TCP session.
     • Slow or overloaded proxy authentication, especially during peak times, can cause intermittent slow loading of UI elements such as organizational charts.
   • Consider proxy scalability: Microsoft 365 services grant multiple long‑term connections per user. Ensure the proxy capacity and authentication infrastructure are sized for this pattern.
7. General client/browser optimization
   • For browser-based views (Outlook on the web, Teams web):
     • Disable unnecessary browser add‑ons.
     • Increase browser cache size.
     • Keep the signed‑in browser session open and avoid unnecessary full reloads.
     • Use tabs and avoid frequent refreshes unless updated data is required.
8. Validate overall bandwidth
   • Use an external speed test (for example, Speedtest) to validate available bandwidth and compare against Microsoft 365 bandwidth planning guidance from the network planning and performance tuning documentation.

These steps help identify whether the prolonged loading of organizational structures is due to DNS, latency, TCP configuration, proxy behavior, or bandwidth constraints. Once the problematic segment (DNS, proxy, or WAN) is identified, traffic to the corresponding Microsoft 365 URLs/IP ranges can be prioritized or optimized using the organization’s network devices and QoS policies.

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References:

• Performance troubleshooting plan for Microsoft 365
• Best practices for using Office 365 on a slow network