Issues triggering emails with attachments from shared mailbox

This article provides a resolution to make sure the flow trigger work as expected for emails with attachments from shared mailbox.

Applies to:   Power Automate
Original KB number:   4563989


In PowerAutomate, when a flow has When a new email arrives in a shared mailbox (V2) trigger, for example, you notice any of the following:

  • The flow isn't triggering for all the emails that come into the mailbox.
  • The flow isn't triggering for emails with attachments.
  • You get a 400 Bad Request or similar error in actions that use the trigger output attachment content bytes.


By default, the trigger will have the following attachment-related options set to No. This is because triggering on all mails doesn't miss any (you might want to trigger on emails without attachments too) and attachments can be large in size:

  • Only with Attachments
    • If set to No, it will trigger on all emails. If Yes, it will trigger on emails with attachments. Use the latter if your flow only needs to trigger on mails with attachments; otherwise, keep it set to No.
  • Include Attachments
    • If set to No, it will not include the attachments content (it will be set to null).
    • For example, if set to No and you have a SharePoint Create File action that uses the null attachment content, then this will result in 400 Bad Request errors because the file content would be null, or empty, which is invalid.
    • If set to Yes, it will include the attachment content bytes instead of being null and SharePoint Create File action, for example, will succeed and the file created will contain the attachment content.


These are the default option values for the trigger output because attachments can be large in size.


To make the flow trigger also on emails that have attachments and to make the attachment content available to other actions (that is, not to set contentBytes to null), in the trigger card:

  1. Expand Show Advanced Options by selecting it.
  2. Set hasAttachments to true.
  3. Set includeAttachments to true.

See associated screenshots for the above steps:

Expand the Show Advanced Options by selecting it:

Screenshot to select the Show Advanced Options item to expand it.

Set Include Attachments to Yes to make the content available to other Power Automate actions.

Set Only with attachments to make the flow trigger only on emails with attachments.

Screenshot shows the options for Include Attachments and Only with attachments.