Sincerely
adverb, < sin-cere-ly >
other words
sincereness ,noun; sincere, adj
meaning: truthfulness, genuineness, straightforwardness
sentences:
1: I am sincerely saying that our vehicle has been roughly used by the driver, so please look at the matter.
2: thank you for your help. sincerely, John.
synonym: artlessly, truly, faithfully.