Power BI Dataflows Microsoft Exchange connector no longer working.

[Robert14358]

i have had this dataflow for 3 years and now it has stopped working for over 2 weeks, It uses the Microsoft Exchange connector.

here is the error:

Error: Data Source Error : DataSource.Error: ErrorInternalServerError: An internal server error occurred. The operation failed.: MashupValueException. RootActivityId = 9754c636-1737-4272-9f61-4a1e1fb22b59.Param1 = DataSource.Error: ErrorInternalServerError: An internal server error occurred. The operation failed.: MashupValueException Request ID: a59c0f49-e431-430b-339a-c700fcc6348e.

If i put the same Query in Power BI Desktop, i get this Error:

Failed to save modifications to the server. Error returned: 'OLE DB or ODBC error: [DataSource.Error] ErrorInternalServerError: An internal server error occurred. The operation failed...

[johnbasha33 · Accepted solution]

Hi  

this pattern (worked for years → now 500/InternalServerError + MashupValueException) is common with the Exchange family of connectors. It usually comes down to one of these:

1. You’re using the older Microsoft Exchange connector against Exchange Online
   That connector is desktop-oriented and doesn’t explicitly target Dataflows. Microsoft now documents Microsoft Exchange Online as the connector that supports Power BI Dataflows (and Dataflow Gen2), while the older “Microsoft Exchange” page only calls out desktop scenarios. Many orgs see intermittent 500s with the old path. Switch the dataflow to Microsoft Exchange Online and re-enter credentials. Microsoft Learn+1

2. Backend/EWS instability or policy changes
   Exchange Web Services (EWS) is being retired in Exchange Online (blocking starts Oct 1, 2026). As Microsoft tightens things, calls that transit old surfaces are increasingly brittle and can surface as 500s. Long-term, Microsoft’s guidance is to move workloads to Microsoft Graph (or connectors that ride it). Microsoft LearnTECHCOMMUNITY.MICROSOFT.COM

3. Auth/CA drift affecting cloud refresh (even if Desktop sometimes works)
   We’ve seen tenants where OAuth/CA changes break Online refresh while Desktop (running under your interactive token) can still enumerate but then fails on save/refresh with the same 500. Microsoft Q&A threads show identical “An internal server error occurred. The operation failed” when OAuth to Exchange is impacted. Microsoft Learn

   Quick fixes to try (in this order)

   1. Clone the dataflow using “Microsoft Exchange Online”

      • In the Dataflow (or Dataflow Gen2) Get Data, pick Microsoft Exchange Online (not “Microsoft Exchange”).

      • Enter the mailbox (user@domain.com) and sign in with your organizational account.

      • Recreate the minimal steps (don’t paste M yet), validate preview, then Save & Close and refresh.
        This connector explicitly supports Power BI (Dataflows) and Fabric Dataflow Gen2, which avoids a bunch of legacy paths that return 500s. Microsoft Learn

        2. Re-enter credentials in the existing dataflow
           Edit Dataflow → Settings → Data source credentials → Edit → sign out/in, pick OAuth/Organizational Account. Then refresh.

        3. Test a minimal Desktop query to isolate service vs. transform
           In a new PBIX: Get Data → Microsoft Exchange Online → pick a tiny table (e.g., Calendar). If even this fails, it’s service/auth; if it works, your old dataflow’s M steps may be hitting a now-unsupported shape (paging/attachments). Microsoft Learn

Check Microsoft 365 Service health (Exchange Online)
Ask your M365 admin to confirm no current Exchange incidents for your tenant/region. (Internal server errors often correlate with transient Exchange backend incidents.)

If you must stay on a custom path, plan a Graph move
If your query relies on specific EWS behaviors, start planning a shift to Microsoft Graph (either via a custom Power Query connector or Web.Contents + OAuth). Microsoft’s own guidance acknowledges many users enabling Graph via custom connectors today.



Did I answer your question? Mark my post as a solution! Appreciate your Kudos !!

@Robert14358

[Anonymous]

Hi @Robert14358,

Just following up to see if the Response provided by community members were helpful in addressing the issue. If one of the responses helped resolve your query, please consider marking it as the Accepted Solution. Feel free to reach out if you need any further clarification or assistance.

Best regards,
Prasanna Kumar

[Anonymous]

Hi @Robert14358,

Just following up to see if the Response provided was helpful in resolving your issue. Please feel free to let us know if you need any further assistance.

Best regards,

Prasanna Kumar

[Anonymous]

Hi @Robert14358

, Thank you for reaching out to the Microsoft Fabric Forum Community, and special thanks to @Shahid12523 and @johnbasha33  for prompt and helpful responses.

Just following up to see if the Response provided by community members were helpful in addressing the issue. If one of the responses helped resolve your query, please consider marking it as the Accepted Solution. Feel free to reach out if you need any further clarification or assistance.

Best regards,
Prasanna Kumar

[Shahid12523 · Accepted solution]

Your Dataflow broke because the old Microsoft Exchange connector is no longer supported.

Fix:

In Dataflow, use Microsoft Exchange Online connector instead.

Re-enter credentials with Organizational account (OAuth).

Long term: migrate to Microsoft Graph (since Exchange Web Services is being retired).

[johnbasha33 · Accepted solution]

Hi  

this pattern (worked for years → now 500/InternalServerError + MashupValueException) is common with the Exchange family of connectors. It usually comes down to one of these:

1. You’re using the older Microsoft Exchange connector against Exchange Online
   That connector is desktop-oriented and doesn’t explicitly target Dataflows. Microsoft now documents Microsoft Exchange Online as the connector that supports Power BI Dataflows (and Dataflow Gen2), while the older “Microsoft Exchange” page only calls out desktop scenarios. Many orgs see intermittent 500s with the old path. Switch the dataflow to Microsoft Exchange Online and re-enter credentials. Microsoft Learn+1

2. Backend/EWS instability or policy changes
   Exchange Web Services (EWS) is being retired in Exchange Online (blocking starts Oct 1, 2026). As Microsoft tightens things, calls that transit old surfaces are increasingly brittle and can surface as 500s. Long-term, Microsoft’s guidance is to move workloads to Microsoft Graph (or connectors that ride it). Microsoft LearnTECHCOMMUNITY.MICROSOFT.COM

3. Auth/CA drift affecting cloud refresh (even if Desktop sometimes works)
   We’ve seen tenants where OAuth/CA changes break Online refresh while Desktop (running under your interactive token) can still enumerate but then fails on save/refresh with the same 500. Microsoft Q&A threads show identical “An internal server error occurred. The operation failed” when OAuth to Exchange is impacted. Microsoft Learn

   Quick fixes to try (in this order)

   1. Clone the dataflow using “Microsoft Exchange Online”

      • In the Dataflow (or Dataflow Gen2) Get Data, pick Microsoft Exchange Online (not “Microsoft Exchange”).

      • Enter the mailbox (user@domain.com) and sign in with your organizational account.

      • Recreate the minimal steps (don’t paste M yet), validate preview, then Save & Close and refresh.
        This connector explicitly supports Power BI (Dataflows) and Fabric Dataflow Gen2, which avoids a bunch of legacy paths that return 500s. Microsoft Learn

        2. Re-enter credentials in the existing dataflow
           Edit Dataflow → Settings → Data source credentials → Edit → sign out/in, pick OAuth/Organizational Account. Then refresh.

        3. Test a minimal Desktop query to isolate service vs. transform
           In a new PBIX: Get Data → Microsoft Exchange Online → pick a tiny table (e.g., Calendar). If even this fails, it’s service/auth; if it works, your old dataflow’s M steps may be hitting a now-unsupported shape (paging/attachments). Microsoft Learn

Check Microsoft 365 Service health (Exchange Online)
Ask your M365 admin to confirm no current Exchange incidents for your tenant/region. (Internal server errors often correlate with transient Exchange backend incidents.)

If you must stay on a custom path, plan a Graph move
If your query relies on specific EWS behaviors, start planning a shift to Microsoft Graph (either via a custom Power Query connector or Web.Contents + OAuth). Microsoft’s own guidance acknowledges many users enabling Graph via custom connectors today.



Did I answer your question? Mark my post as a solution! Appreciate your Kudos !!

@Robert14358