Guess which is the error:
In email after email (including two this morning), I find people incorrectly capitalizing the complimentary close. The rule is to capitalize only the first word of the close. This rule applies wherever you use a complimentary close: emails, letters, notes, and even texts. These are all correct:
With deep sympathy,
The complimentary close isn't a title or a heading, so there's no need to capitalize all the nouns or important words--just the first word, whatever it is.
Note: Sometimes people refer to the complimentary close as the salutation. Don't let them fool you. The salutation is the greeting.
Have other capitalization errors caught your attention? Please share them.