400 "unable to deserialize" / "error parsing request body" when calling messages.send

Question and Answers
1

Hi,

I’m sending email with the Node SDK (nylas@8.0.5) and I keep getting a 400 from messages.send.

Provider/API side error (Microsoft):

400 unable to deserialize
error parsing request body

I’m using the v8 SDK like this:

await nylas.messages.send({
identifier: grantId,
requestBody: {
from: [{ name: 'Sender', email: 'sender@example.com' }],
to: [{ name: 'Recipient', email: 'recipient@example.com' }],
replyTo: [{ name: 'Reply', email: 'reply@example.com' }],
subject: 'Test',
body: '<p>Hello</p>',
},
})

Request id where i’ve got this error first today is: 3431756385-1e4739b8-9659-469e-98b7-a5a32acb2304

I also tested without replyTo and still got the same error. No attachments are used.

A few questions:

  1. Are there known cases where Nylas returns provider returned error + unable to deserialize even when the JSON looks valid?

  2. Is there a way to get the raw request validation error from Nylas, or more detailed provider-side diagnostics?

  3. Maybe a bug in Nylas to Microsoft integration somewhere?

Thanks.

2

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