The phrase "a letter that includes" is correct and usable in written English.
You can use it when referring to a letter that contains specific information or details.
Example: "Please send me a letter that includes your updated contact information."
Alternatives: "a letter containing" or "a letter with".
In that context, you handed me a letter that includes very important statements regarding Israel's security and its well-being as a Jewish state.
The Brexit campaign group backed by the justice secretary, Michael Gove, is trying to persuade senior NHS staff to sign a letter that includes a direct attack on David Cameron, who is accused of having starved the health service of funding.
In this case, if you believe you're right, pull together the necessary documentation and send it back to the IRS through certified mail within 30 days, along with a letter that includes a copy of your correspondence audit and your "reference number" (the case number that appears in the letter you received).
Women with a result in the normal range receive a letter that includes an offer to speak to a genetic counsellor at their local clinical service should they require further information.
In a typical minimal intervention [ 24- 26], a GP may advise patients to discontinue long-term BZD use without medical assistance by sending a letter that includes information on the negative consequences of continued use and guidelines on withdrawal.
In an attempt to resume the process, the management team sent the union negotiators a letter that included an apology.
Last spring, the city's deputy prosecutor received a letter that included the line, "We cannot be governed by clowns and fags".
As for the letter accusing Israel of "collective punishment" on the Gaza blockade, he did sign a letter that included that phrase but it did not accuse Israel of using collective punishment (in fact, Mr. Sestak supported the blockade).
Last fall, George J. Tenet, the director of central intelligence, briefly sparked a political controversy when he provided Congress with a letter that included declassified portions of a C.I.A. assessment that Iraq would be more likely to resort to terrorism if attacked.
Because Dr. Hamer told Mr. Sawyer that he was looking for up to 2,000 students to try out the materials, the superintendent sent Dr. Hamer a letter that included a list of the district's 10 largest schools.
When he learned that I was close to quitting my eighth-grade basketball team mid-season, he typed a letter that included a story about his hapless experience trying out for the Holy Cross basketball team.
