I just got an email from authorize.net that they are making changes that impact transactions. I assume you are on top of the changes Authorize.net is making but would like confirmation that you don't need anything from us.
Yes, we're on top of these changes, and the email you received is simply a reminder of messages they have already sent. You can read more about these changes here:
A copy of the email you received is most likely similar to the one we received.
Please let us know if you have any more questions by submitting a Support Request. Thank you.