Yvonne Mason knows a few things about grammar. She taught English composition for 17 years in South Carolina public schools. Mason has since retired, but the veteran teacher recently received a letter that she had to publicly call out for its "stylistically appalling" prose.

It was a missive sent by the White House, signed by President Trump.

Earlier this month, Mason shared a photo of the letter, covered in purple ink and blunt editorial critiques.

Got a letter from Mr. Trump. Will be returning it tomorrow. Posted by Yvonne Mason on Monday, May 14, 2018

"Have ya'll tried grammar and style check?" Mason wrote at the top of the letter, punctuated by two asterisks.

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"OMG this is WRONG!" she wrote at the bottom, citing one of many incorrect uses of capitalization.

Mason told the Greenville News she received the letter from the White House after writing a note to the president, urging him to meet with the families of the victims of the Parkland, Florida, school shooting.

She conceded that she knew a White House staffer -- not Mr. Trump himself -- probably crafted the letter. But Mason could not contain her disappointment in its quality.

"When you get letters from the highest level of government, you expect them to be at least mechanically correct," Mason told the Greenville News.

Mason also seemed to take issue with the overuse of the "I" in Mr. Trump's letter, as evidenced by the pronoun being highlighted five times in yellow.

"If it had been written in middle school, I'd give it a C or C-plus," Mason told the newspaper. "If it had been written in high school, I'd give it a D."