Might sound freakish, but put yourself in the other person's shoes, who proposed you and naturally expected a 'yes' initially. You didn't respond, and the person anticipated intuitively that a 'no' might be coming his/her way. But you didn't say that either.
Or, you had a correspondence with someone, and later realized that he or she is not the ideal match for you. But you abstained from saying 'no' for the fear that you sound callous. Or, you got married, and the people, you had been having correspondence with, are still hunting for you on the site!
The perplexity of no response at all could be really excruciating to someone. It'll always be considerate and humane on your part to say a 'no' when you know you are not going to say yes. No doubt, it's always a tough call to turn a proposal down while sounding sympathetic, for the word 'no' in its very essence is a harsh statement. Yet, a little bit of maneuvering and tact will be get the desired upshot.
Here are a few mock-up messages for different situations/stages of correspondence that you can play around with and send, so that you can "Deny with Dignity":
Dear____________________ ,
The little correspondence we had was really nice and gave both of us a chance to have an insight into each other's persona. However, I feel that we don't make an ideal match.
I wish you good luck in your partner search.
With regards,
____________________ ,
Dear____________________ ,
It was nice to communicate to you. And it was through this little correspondence that I inferred that we are not ideally suited to each other. So terminating the correspondence right here will be better for the matrimonial quest of both of us.
Best of luck for your matrimonial quest.
With regards,
____________________ ,
Dear____________________ ,
We really shared a truly wonderful nexus and I really enjoyed the interaction we had.
However, it was through this correspondence and exchange of ideas that gradually made me realize that we differ in general outlook about life and are two very different persons. Continuing this relation further is not going to do any good so we'll be better off bringing our correspondence to an end.
I hope you understand, as you have always been very understanding and considerate.
I wish you all the best of luck in your quest for a dream mate.
With regards,
____________________ ,
Dear____________________ ,
We really had a wonderful nexus and the correspondence we had was nice. However, having known you so closely, I concluded that our relation cannot translate into wedlock, since we are not ideally suited. I hope you understand.
I wish you all the best in your search for a dream mate.
With regards,
____________________ ,
Dear____________________ ,
I have found a life partner for myself and we are about to marry soon. I thank you for the amazing nexus we shared and I must say it was really great to know a person like you.
Wishing you all the best in your partner search,
With regards,
____________________ ,
Dear____________________ ,
Finally, my search for a dream mate is over! I've found a suitable match and we are about to marry soon. Congratulate me! Also, I thank you for the wonderful nexus we shared.
I wish you all the best in your life partner quest.
With regards,
____________________ ,
Remember, the way you say is sometimes more important than what you say.