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.
See this article for tips on capitalizing common message greetings, such as “Good morning“.