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Workaround to the problem in the dataflow – “We did not recognize the format of your first file”


Using Microsoft Exchange Online connector, we can connect to an Exchange mailbox account and extract email contents into Power Query. However, when we filter some CSV files from the mail attachments and want to combine them into one query, a message pops up saying “We didn’t recognize the format of your first file. Please filter the list of files so it contains only supported files (Text, CSV, Excel, workbooks, etc.) and try again.”


These files are all CSV files and have the same table structure. If we click on any Binary content in a cell, it will navigate to the file and extract all data into Power Query correctly from the CSV file. So this operation should be supported.


Repro Steps

  1. Send an email to one’s Exchange mailbox with two CSV files as attachments. These files have the same table structure.
  2. Go to, enter a workspace and create a dataflow.
  3. Create a new query and connect to the same mailbox account using Microsoft Exchange Online connector.
  4. Select Mail, filter the email with CSV attachments, expand Attachments column and select AttachmentContent.
  5. Click combine icon on the header of AttachmentContent column. Wait a while and you will see below dialogue.





Power BI Service version13.0.15854.62



Since this problem does not occur in Power BI Desktop, we can first connect to the same mailbox account in Power BI Desktop with Microsoft Exchange Online connector, extract the AttachmentContent column and combine all CSV files into one query in Power Query Editor. Then copy this query and paste it in Power Query Online. Then this query can be saved in the dataflow without any problem.




Author: Jing Zhang

Reviewer: Kerry & Ula