Grammar and Orthography.
These should receive most careful attention. “A great author is one,” according to Taine, “who, having passions, knows also his dictionary and grammar.” And a good letter-writer, as well, must “know his dictionary and grammar” to render his missives presentable.
Grammatical errors are almost unpardonable, and a misspelled word is an actual crime in these days of dictionaries. Punctuation and capitalization, too, must be looked after, and the whole letter give evidence of thought and care on the writer’s part.