How to make a POST HTTP call using the text content of an email attachment as request body ?

[muzietto]

I am trying to build a simple flow: when an email with a given title arrives in my mailbox an HTTP POST call must be made, using the text inside the email attachment as body of the request.

I've taken care of all the aspects:

• the email comes from an automatic process and the title is guaranteed to be correct
• the email contains always an attachment
• the attachment is a text file in CSV format, which can be sent with mimetype "text/csv"

Nevertheless I am unable to specify in the flow editor that the attachment text must go into the body.

I have tried several options in the graphic editor, but I can never save the flow.

Example error message at save is: Save flow failed with error code 'OpenApiOperationParameterValidationFailed' and message 'Input parameter 'Body' validation failed in workflow operation 'Send HTTP Request': The parameter with value '"@triggerOutputs()?['body/hasAttachments']"' in path 'Body' with type/format 'Boolean' is not convertible to type/format 'String/binary'.'.

I presume that I need to write some code to run inside the task and prepare the request execution programmatically. Anyone has a suggestion on how to handle this case?

[PowerAppsWizard]

Hi,

The property hassttachments is only indicating if the email has an attachment or not (as true / false). It is not the actual file content.

I believe u would need store the attachment e.g. Sharepoint and than get file content action and use for the body.

[muzietto]

Thank you for your comment. I have checked around and it seems that this manner of operating through attachment storage on Sharepoint is quite common. However, it means introducing a third component (on top of email service and http service) while I have the attachment already in my hands.

I have a crucial question, actually three questions:

• do you know if there is already a task that retrieves a file from Sharepoint and reads its content? I would put it in front of the HTTP task and provide the text to the HTTP body
• do you know any tutorial that explains how to build a 100% custom Power Automate task? If I google around I find tutorials on making specific tasks (a mining task, a planner task, etc.) - I'd like to understand the programming language underlying all this and try to manipulate my email and extract its attachment text by programming (setting variables, etc.)
• better yet: is there already a simple task that reads a file (the email attachment) and returns its content?

Thank you for your attention. Cheers.

[muzietto]

I have made some progress, by discovering and using the "Get Attachment" action. Now I am still struggling to READ the attachment content and having it available as the value of some variable. Once done that, I'd like to put that variable as input in the "Body" field of the HTTP post and things should work.

But HOW???

[Expiscornovus · Accepted solution]

Hi @muzietto,

You probably need to turn the encoded value to string first.

Below is an example

1. In this sample a Filter Array is included to check for text/csv type of attachments (in case you receive multiple attachments in one email). You can add this via advanced mode.

@equals(item()?['contentType'], 'text/csv')

2. The apply to each uses the Body of the Filter array, which should only contain csv files

3. The HTTP request uses the string version of the attachment content bytes. The below expression is used to convert the base64 encoded content to a string.

base64ToString(outputs('Get_Attachment_(V2)')?['body/contentBytes'])

You can add that expression via the expression editor.

[muzietto]

This is great stuff, THANK YOU !!

[muzietto]

@Expiscornovus  - I am trying to implement the flow you described, but I am continuously clashing with a problem. I described it in another post: https://powerusers.microsoft.com/t5/Building-Flows/Cannot-modify-criteria-of-foreach-loop-the-foreac...

Wat ben ik verkeerd aan het doen?

[Expiscornovus]

Hi @muzietto,

In that other thread you are using the below expression:

outputs('Select_only_CSV_attachments')['body/attachments']

Are you also using the Filter Array action? If not, you can use the below in the foreach, that data is coming from the trigger action, in that case you use the triggerOutputs function:

triggerOutputs()?['body/attachments']

If you are using the Filter Array action as well, make sure you use the below body function and not refer to the attachments property specifically. In the Filter Array we are already using the attachments property in the From field, so the outputs won't contain that property.

body('Filter_array')