'flowers were gorgeous! Thank you so much also for prompt delivery.'
'I want to thank you for trying to reach me. I did not get your message till late Monday night, and did not see your email until today. I am sure you guys replaced the flowers I ordered for my cousin...Thank you again..'
'Very good service and consideration. Thank you.'
You won't be able to dismiss this by usual means (escape or click button), but you can close it programatically based on user choices or actions.