🐛 Bug Report — Runtime APIs Error: "In-Reply-To does not match original Message-ID" for MS Outlook emails

[asimpletune]

Send an email to a CF worker from a MS outlook client and try to reply using the email's Message-ID. This happens with the exact same code from the docs, and then you'll find the following error:

Error: In-Reply-To does not match original Message-ID

[asimpletune]

I can confirm that prepending a line break to ms outlook message_id's fixes the issue, but it's still a bug.

reply_msg.setHeader('In-Reply-To', `\n ${msg.headers.get('Message-ID')}\n`) // notice the \n

[asimpletune]

Here is an example message-id that fails

Message-ID:
 <PAXP193MB2314C6F90A60DA909597069AA7802@PAXP193MB2314.EURP193.PROD.OUTLOOK.COM>

This comes from the actual source of an email sent by ms outlook. It looks like there's some line folding that is happening. I'm guessing that on the cloudflare end of things, the string is being compared to the original message exactly. However, the header.get method returns the header value without the folding.

I think the email specs allow folding but that the unfolded text should be treated as one line.