Windows 10 Mail Program Bug: Ignores Reply-To Header

Some Replies go to the Wrong Email Address

Here’s the scenario: Online response forms on websites often send email using a common predefined “From: address” to ensure delivery through spam filters, and using an email address for the website owner as the “To: address”.

They also use a Reply-To header to direct replies back to the end-user who filled in the online form. This is a very standard method of handling emails from online forms.

Example

  • To: sales@website-owner.com
  • From: online-form@server.com
  • Reply-To: end-user@gmail.com
  • Subject: Request for Quote

The website owner receives the user’s request via an email message, and when the website owner clicks REPLY in their email program, a reply is supposed to be sent back to the end-user who sent the request. Simple.

This works for all known email clients EXCEPT if the website owner is using the Windows 10 mail client.

The Windows 10 mail client appears to ignore the Reply-To header in the received email message, and when it replies to such an email message, it always sends the reply to the email address on the From: header instead of sending it to the email address on the optional Reply-To header when the Reply-To header is present and populated.

In short, the Windows 10 mail client does not follow the RFC standard and it does not send replies to the proper recipient in this situation.

Using the above example, all other email clients would send the reply to end-user@gmail.com, except the Windows 10 mail client sends the reply to online-form@server.com (an unmonitored destination) meaning that the end-user never receives the reply and the website owner doesn’t know that his reply will never be seen.

Windows Support

Please fix the Windows 10 mail client’s broken behavior when deciding what email address to send replies to when a Reply-To header is present and populated in the original email message.

This bad and unexpected behavior has been occurring for months. Please fix.

Thank you.

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