Dynamics 365 WebApi - BATCH request - Error - The message header ' ' is invalid - dynamics-crm

Question

Anyone is facing the follow error message, trying to execute a BATCH request for Dynamics 365 WebApi? I'm using Postman.
{
"Message": "The message header ' ' is invalid. The header value must be of the format '<header name>: <header value>'.",
"ExceptionMessage": "The message header ' ' is invalid. The header value must be of the format '<header name>: <header value>'.",
"ExceptionType": "Microsoft.OData.ODataException",
"StackTrace": " at Microsoft.OData.MultipartMixed.ODataMultipartMixedBatchReaderStream.ValidateHeaderLine(String headerLine, String& headerName, String& headerValue)\r\n at Microsoft.OData.MultipartMixed.ODataMultipartMixedBatchReaderStream.ReadHeaders()\r\n at Microsoft.OData.MultipartMixed.ODataMultipartMixedBatchReaderStream.ProcessPartHeader(String& contentId)\r\n at Microsoft.OData.MultipartMixed.ODataMultipartMixedBatchReader.SkipToNextPartAndReadHeaders()\r\n at Microsoft.OData.ODataBatchReader.ReadImplementation()\r\n at Microsoft.OData.ODataBatchReader.InterceptException[T](Func`1 action)\r\n at Microsoft.Crm.Extensibility.OData.CrmODataBatchHandler.<ParseBatchRequestsAsyncImplementationAsync>d__16.MoveNext()\r\n--- End of stack trace from previous location where exception was thrown ---\r\n at System.Runtime.ExceptionServices.ExceptionDispatchInfo.Throw()\r\n at System.Runtime.CompilerServices.TaskAwaiter.HandleNonSuccessAndDebuggerNotification(Task task)\r\n at Microsoft.Crm.Extensibility.OData.CrmODataBatchHandler.<>c__DisplayClass9_0.<<ParseBatchRequestsAsync>b__0>d.MoveNext()\r\n--- End of stack trace from previous location where exception was thrown ---\r\n at System.Runtime.ExceptionServices.ExceptionDispatchInfo.Throw()\r\n at System.Runtime.CompilerServices.TaskAwaiter.HandleNonSuccessAndDebuggerNotification(Task task)\r\n at Microsoft.PowerApps.CoreFramework.ActivityLoggerExtensions.<ExecuteAsync>d__11`1.MoveNext()\r\n--- End of stack trace from previous location where exception was thrown ---\r\n at System.Runtime.ExceptionServices.ExceptionDispatchInfo.Throw()\r\n at System.Runtime.CompilerServices.TaskAwaiter.HandleNonSuccessAndDebuggerNotification(Task task)\r\n at Microsoft.Xrm.Telemetry.XrmTelemetryExtensions.<ExecuteAsync>d__6`1.MoveNext()\r\n--- End of stack trace from previous location where exception was thrown ---\r\n at System.Runtime.ExceptionServices.ExceptionDispatchInfo.Throw()\r\n at System.Runtime.CompilerServices.TaskAwaiter.HandleNonSuccessAndDebuggerNotification(Task task)\r\n at Microsoft.Crm.Extensibility.OData.CrmODataBatchHandler.<ParseBatchRequestsAsync>d__9.MoveNext()\r\n--- End of stack trace from previous location where exception was thrown ---\r\n at System.Runtime.ExceptionServices.ExceptionDispatchInfo.Throw()\r\n at System.Runtime.CompilerServices.TaskAwaiter.HandleNonSuccessAndDebuggerNotification(Task task)\r\n at System.Web.OData.Batch.DefaultODataBatchHandler.<ProcessBatchAsync>d__0.MoveNext()\r\n--- End of stack trace from previous location where exception was thrown ---\r\n at System.Runtime.ExceptionServices.ExceptionDispatchInfo.Throw()\r\n at System.Runtime.CompilerServices.TaskAwaiter.HandleNonSuccessAndDebuggerNotification(Task task)\r\n at System.Web.Http.Batch.HttpBatchHandler.<SendAsync>d__0.MoveNext()",
"ErrorCode": "0x0"
}
Image of Postman headers
Here's my Body Content:
--batch_AAA123
Content-Type: multipart/mixed;boundary=changeset_BBB456
--changeset_BBB456
Content-Type: application/http
Content-Transfer-Encoding:binary
Content-ID: 1
POST https://copasa.crm2.dynamics.com/api/data/v9.1/tasks HTTP/1.1
Content-Type: application/json;type=entry
Accept: application/json
{"subject":"Task 1 in batch","regardingobjectid_account_task#odata.bind":"https://copasa.crm2.dynamics.com/api/data/v9.1/accounts(1AD045E1-7DE4-E911-A812-000D3AC058C3)"}
--changeset_BBB456
Content-Type: application/http
Content-Transfer-Encoding:binary
Content-ID: 2
POST https://copasa.crm2.dynamics.com/api/data/v9.1/tasks HTTP/1.1
Content-Type: application/json;type=entry
Accept: application/json
{"subject":"Task 2 in batch","regardingobjectid_account_task#odata.bind":"https://copasa.crm2.dynamics.com/api/data/v9.1/accounts(1AD045E1-7DE4-E911-A812-000D3AC058C3)"}
--changeset_BBB456--
--batch_AAA123
Content-Type: application/http
Content-Transfer-Encoding:binary
GET https://copasa.crm2.dynamics.com/api/data/v9.1/accounts(1AD045E1-7DE4-E911-A812-000D3AC058C3)/Account_Tasks?$select=subject HTTP/1.1
Accept: application/json
--batch_AAA123--

Answer 1

Nothing looks wrong except the extra white lines between Batch request unique identifier & headers, the error maybe coming because of that. Remove the extra white lines like below:
--batch_AAA123
Content-Type: multipart/mixed;boundary=changeset_BBB456
--changeset_BBB456
Content-Type: application/http
Content-Transfer-Encoding:binary
Content-ID: 1
POST https://copasa.crm2.dynamics.com/api/data/v9.1/tasks HTTP/1.1
Content-Type: application/json;type=entry
Accept: application/json
{"subject":"Task 1 in batch","regardingobjectid_account_task#odata.bind":"https://copasa.crm2.dynamics.com/api/data/v9.1/accounts(1AD045E1-7DE4-E911-A812-000D3AC058C3)"}
--changeset_BBB456
Content-Type: application/http
Content-Transfer-Encoding:binary
Content-ID: 2
POST https://copasa.crm2.dynamics.com/api/data/v9.1/tasks HTTP/1.1
Content-Type: application/json;type=entry
Accept: application/json
{"subject":"Task 2 in batch","regardingobjectid_account_task#odata.bind":"https://copasa.crm2.dynamics.com/api/data/v9.1/accounts(1AD045E1-7DE4-E911-A812-000D3AC058C3)"}
--changeset_BBB456--
--batch_AAA123
Content-Type: application/http
Content-Transfer-Encoding:binary
GET https://copasa.crm2.dynamics.com/api/data/v9.1/accounts(1AD045E1-7DE4-E911-A812-000D3AC058C3)/Account_Tasks?$select=subject HTTP/1.1
Accept: application/json
--batch_AAA123--

Answer 2

I had the same problem only it was saying that the message header '\t' was invalid. On one of my blank lines I had tab character that I couldn't see. Once I found it and removed it, my request went through just fine.