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Sending fax via the api is sending a blank page with a watermark
Tags: sdk
Dec 4, 2020 at 1:22pm   •   6 replies  •  0 likes
Bruce Ganek

I'm in the sandbox, writing using the C# SDK. I can programmatically send a fax to the requested number but it appears with no attachment and the cover page has a watermark through it saying - "test fax using ringcentral development account"

What am I missing to transition it to the actual fax while in the sandbox environment?

Thank you.

6 Answers
answered on Dec 8, 2020 at 8:23am  

Well, that makes me feel better that I didn't mess up.

Can you let me know the best way to send a pdf? I have the commented code in my previous email, but then saw the comment about creating a multipart and attaching the PDF, I'm not sure how to do that if that's the way I need to do it.

Since I can't check it right now until I go to production, I'm trying to make sure I'm in good shape first.

Thank you,


answered on Dec 8, 2020 at 7:52am  

Hello, thank you for your help.

I have stripped down the program to just send text as an attachment. I'm sending it from the developer's account in RingCentral to my actual Ring Central phone number on my computer.

When I send it, the cover page says I have 2 pages, but only one is coming through.

Here is my current code.

Byte[] myBytes = File.ReadAllBytes("testing.pdf");

//ar attachment = new Attachment { fileName = "testing.pdf", contentType = "application/pdf", bytes = myBytes };

var attachment = new Attachment { fileName = "test.txt", contentType = "text/plain", bytes = Encoding.UTF8.GetBytes("hello world") };

var attachments = new Attachment[] { attachment };

sendFaxMessageRequest.attachments = attachments;

sendFaxMessageRequest.coverPageText = "this is Bruce's Test";

var r = await rc.Restapi().Account().Extension().Fax().Post(sendFaxMessageRequest);

Also, will the commented out part work for sending a PDF (i.e. the content type and readallbytes) once I get attachments working.

I saw this but I'm unclear how to do it and have been unable to find a sample, can you steer me in the right direction?


To send a fax you'll need to create a multipart/mixed request and add each PDF as an attachment. You can either send the raw bytes or base 64 encode the file.


Thank you

answered on Dec 8, 2020 at 8:13am  

Hi Bruce,

Sending fax from a sandbox account is currently broken. It is the problem as you are facing now, no attachment. I created a Jira ticket some time ago but it is still not resolved yet. Meanwhile, fax works correctly in the production environment. I will check the ticket and push for fix asap.

answered on Dec 8, 2020 at 10:20am  

I believe that it must be as simple as this

var attachment = new Attachment { fileName = "test.pdf", contentType = "application/pdf", bytes = System.IO.File.ReadAllBytes("test.pdf") };
var attachments = new Attachment[] { attachment };
requestParams.attachments = attachments;

answered on Dec 8, 2020 at 10:44am  

Sounds good, that's what I was doing, I just can't see if it is correct currently in the sandbox.

Thanks for all of your help.


answered on Dec 5, 2020 at 2:02am  

It maybe due to the reason that your attachment files are not getting attached properly.

Can you please refer the following:


and see if this helps your issue


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