"Thanks for your mail. It is a very kind gesture of yours that my email address still exists in your database.
You might have written it in a good faith and as a normal routine but I want to mention that I do not deserve these words of praise and felicitation, because I was never given an opportunity by you (except once), to extend my 'cooperation' or have 'working relationship' with you, (or prove my efficiency, if you allow me to say), which I earnestly desired to, honestly.
It might be strange for you to know and you might have forgotten it, that after entering the world of online translation (2006), my very first (paid) translation assignment, which I feel proud of, was with YOU. If you don't believe, I can provide you with the copies of your mails together with that medical assignment which concerned Diabetes.
I am not writing to you this for seeking any work etc, but just to thank you only for your courtesy and paying a raw person at that time which boosted my confidence too much. I am well established now by the grace of Almighty (http://www.proz.com/profile/133882), but I still remember your company that how afraid I was dealing with you because it was my first time.
Anyhow, thanks for giving me your time for reading all this, which I could not resist writing when I saw your name at the bottom of your mail
May God bless you, Sir !"