"Yours faithfully" is an old-fashioned phrase that has been commonly used in business letters to sign off. However, with the ever-evolving English language, there are now more alternatives to this traditional closing. Some suitable synonyms include "Sincerely," "Yours truly," "Best regards," "Kind regards," "Warm regards," "Respectfully," "Cordially," "With appreciation," and "With gratitude." These synonyms express politeness and respect while conveying the right level of formality. It is important to choose the closing phrase that best suits the relationship between the writer and the recipient, and the context of the letter itself.