Hi Liz
Im not sure what the actual rate of what is acceptable but 90% seems to be ok. What you can do, is click on the HELP section of Airbnb and type in the subject matter of RESPONSE RATE. I myself have a 100% rate and always have now for 7 months. I also suggest that you download the Airbnb app to your smartphone (if you have one) and respond to everyone within a few hours or less if you can. I personally respond to every booking request within 10-15 mins. It does help that I have a smartphone too. You only have 24 hours to respond which is a lot of time to get back to someone. All that means, is to write them back as quickly as possible. Ask the questions you need in order to decide on accepting or decline. but be careful on how many times you decline too.
Im surprised you got that notification but you certainly have time to fix that rating. Try very hard to respond much quicker and you will see the reponse rate go up in 30 days. Hope I was helpful. If you dont' find the answer you need in that article, you can always reach out to the Airbnb customer service phone line, the staff there is amazing. They can help you walk through what that notification was truly about. Im sorry you are worried about this but you have the opportunity to turn it around. Good Luck
If you feel that me or another host have helped you, feel free to click on the "thumbs up" button at the end of any post. Thank you so much.
Aloha, Momi
Great way to contact Airbnb or via Twitter at AirbnbHelp / Facebook