I am not so sure. Can you tell us what do you want to apologize for?
This way you are not apologizing, but just thanking someone, although it might be possible to interpret it as an apology in a certain context. So give us yours!
Hello again, I heard that in a Czech plane when the flight was delayed and then again read it in an email where the writer was thanking for understanding to a man who bought something from him on EBay and the writer never sent the item to him,
thank you again,