Thank you for thatWe had the same thing. My sponsor had the AFP check done, we uploaded it to our ImmiAccount and emailed them at the email address at the bottom just to confirm that that's all they needed for now as I'll be leaving Australia soon.
They responded saying that they received it and they have progressed our application on to the next stage.
I don't think you actually have to write to them because if you look at the letter it says:
"You must respond to this request for additional information within 28 days after you are taken
to have received this letter. You should provide your response in writing.
You can upload your response to your ImmiAccount.
Alternatively you may send the information and/or documents by mail to
Permanent Partner Processing Centre - Victoria
Sponsorship Assessment Unit
Department of Immigration and Border Protection
GPO Box 241 Melbourne VIC 3001"
Your response in writing is what they're asking for; the police clearance so uploading this to the immi account should suffice
I uploaded the AFP document to my immiaccount then emailed
[email protected] as this is the only one they mentioned in their letter, I received an automatic reply that they will reply to my email within 2 weeks if it was relevant. Though I haven't received any email to confirm that they have received my AFP.