[Toybox] Fwd: [Update] Gmail will start rejecting some messages that are non-compliant with internet message format standards as of Apr. 24, 2023

[Rob Landley]

Heads up, sounds like gmail will no longer be able to receive mailing list
messages after April. (I really gotta move my personal email to dreamhost's
server...)

Rob

-------- Forwarded Message --------
Subject: 	[Update] Gmail will start rejecting some messages that are
non-compliant with internet message format standards as of Apr. 24, 2023
Date: 	Thu, 23 Mar 2023 08:30:56 -0700
From: 	The Google Workspace Team <workspace-noreply at google.com>
Reply-To: 	The Google Workspace Team <workspace-noreply at google.com>
To: 	rob at landley.net

Gmail is taking measures to better protect Gmail customers from spam and abuse.

Dear Administrator,

We’re writing to let you know about an upcoming change to your Gmail services.
Gmail will start rejecting messages that are non-compliant with Internet Message
Format standards and contain more than one single-instance email header as of
*April 24, 2023*.

You are receiving this message because during February 2023, your organization
has either sent or received more than 10 emails with duplicate headers.


      What does this mean for your organization?

If your users are currently sending messages with multiple headers, the messages
will start being rejected with the error message: “This message is not RFC 5322
compliant,” starting*April 24, 2023.*

For context, email headers are a set of lines that precede the body of an email
message. They contain information about the sender, recipient, subject, the
message's route to the recipient's inbox, and how to interpret the body (text,
html, image). They also provide information that can be used to verify the
authenticity of a message. Therefore, rejecting messages that contain more than
one single-instance email header proactively prevents malicious duplicate header
exploitation, and email spam.

The Internet Official Protocol Standards: Internet Message Formats
[Request For Comments (RFC) 5322] states that a message must have*at most one
instance of each of the following headers:*

  * |To|
  * |Cc|
  * |Subject|
  * |Date|
  * |From|
  * |Sender|
  * |Reply-To|
  * |Bcc|
  * |Message-ID|
  * |In-Reply-To|
  * |References|

*Note:* Please see RFC Editor’s
Internet Message Format RFC 5322 document
for additional information on the headers that are standards-compliant.

      What do you need to do?

We recommend sharing this message with your users to avoid being impacted by
this effort. For more information on support please see Prevent mail to Gmail
users from being blocked or sent to spam [four line long tracking URL removed].

We thank you for your patience and understanding as we make this important change.

Thanks for choosing Google Workspace.

*– The Google Workspace Team*