Not all thank-you notes are created equal.

After lunching with Sen. Rand Paul, R-Ky., on Capitol Hill earlier this month, Republican super-donor Foster Friess emailed the White House hopeful a personal note thanking him for his time and for hosting him in the Senate dining room, “my favorite D.C. place to be fed.” But Paul wasn’t the only senator on the other end of Friess’ correspondence, nor were the topics limited to the Senate bean soup.

In a copy of the email obtained by the Washington Examiner, Friess, a highly successful investment manager known for his generous support of conservative and Christian causes, gently scolded Paul’s libertarian foreign policy, especially his reticence toward more active U.S. leadership in the Middle East. Friess didn’t keep the criticism private, either, informing Paul that he had “BCC’d” four other Republican senators on the email. Among them: Ted Cruz of Texas, considered Paul’s chief rival for the anti-Establishment vote in the 2016 primary field.

A spokesman for Cruz declined to comment on the email. In the note, Friess, who was unavailable for comment, specifically urges Paul to support sending more U.S. aid to the Kurds in the battle against the Islamic State.

Possibly motivating the multimillionaire to publicize his critique of Paul: Friess plans to back Rick Santorum for president in 2016. In the 2012 campaign, Friess almost single-handedly bankrolled the former Pennsylvania senator's super PAC, the Red, White and Blue Fund.

“Rand, I respect your reluctance to put Americans in harm's way by providing doctors, nurses, and mechanics to fix busted axles, technicians to deactivate booby traps, anti-tank weapons and personnel to protect them. (Anti-war liberals can support these measures.) But I wish I could dissuade you,” Friess wrote.

“Maybe you are influenced by those who believe, ‘They are all crazies over there, so why not stay out and let them kill each other?’ It is understandably confusing to sort the good guys from the bad guys,” Friess continued. “America’s blocking aid to the Kurds embarrasses me — No, I am ashamed.”

It’s not all that unusual for the political donors who writes big checks to speak frankly to potential presidential candidates. Their wallets, and Rolodexes chock full of similarly wealthy associates, are coveted by likely 2016 candidates as they ready their political operations for the primary. Part of the major donor interview process involves listening the donor's concerns.

Friess, 74, isn’t your typical GOP Establishment donor. The businessman and investor is a something of a conservative activist. He’s conservative on social, fiscal and national security policy, and he isn’t shy about sharing his views in public, as many Republican moneymen tend to be.

Still, it’s out of the ordinary that someone like Friess would use a private conversation to publicly unload on a sitting U.S. senator and possible major contender for the presidency.

Copied on the email were Republican Sens. Lamar Alexander of Tennessee; Roy Blunt of Missouri; Lindsey Graham of South Carolina, who is exploring a run for president; and Cruz. In the correspondence, Friess mentions Graham and thanks him for “hosting my invitees in his conference room last Thursday to hammer out his ‘Kurdish Emergency Relief Act,’ which he intends to introduce with $500,000,000 of funding.”

Paul’s office had not responded Tuesday for a request for comment. But Friess’ criticism revealed the challenge the Kentucky Republican could face in 2016. The rise of the Islamic State and a belligerent Russia under Vladimir Putin could lead to a campaign that is defined by national security. Early indications suggest a consensus among GOP primary voters for a hawkish leader who believes in stronger U.S. leadership abroad. The full email (spelling and usage not corrected) follows below:

From: Foster Friess <<i> ff@fosterfriess.com>

</<i> ff@fosterfriess.com>

Date: February 11, 2015 at 9:04:11 PM CST

To: xxxx.xxxxx<<i> jessica_jelgerhuis@paul.senate.gov>

</<i> jessica_jelgerhuis@paul.senate.gov>

Subject: Rand (Paul), thanks for lunch Thursday..

…..with you and your Chief of Staff, Doug Stafford. The Senate dining room is my favorite D.C. place to be fed. Great to see Senators Roy Blunt and Lamar Alexander both of whom I have blind “cc’d” so they can get in the loop on efforts to protect the Kurds.

Also bcc’d is Ted Cruz, thanking him for so quickly responding to the meeting I had with him by articulating later that day on CNN the need to supply the Kurds directly.

Also bcc’d, Rand, are a number of others who want to be part of ending the beheadings by arming the Kurds directly. (Anyone wanting off the list, contact judy@fosterfriess.com.)

Thanks to Lindsey Graham (also bcc’d) for hosting my invitees in his conference room last Thursday to hammer out his “Kurdish Emergency Relief Act,” which he intends to introduce with $500,000,000 of funding. What does Obama’s request for use of force do to Lindsay’s idea?

Invitees included Katie and Sebastian Gorka, counterterrorism experts, (Sebastian chairs war theory department at the Marine Corps University); Tawfik Hamid, Muslim reformer formerly associated with Ayman al-Zawahiri and violent Jemaah Islamiyah terrorist group. Wyoming U.S. Senator and member of Senate Foreign Relations committee, John Barrasso; Awat Mustafa, Kurdish executive with Barzani Charity Foundation ; and, Tulsi Gabbard, second term Democrat of Hawaii’s 2nd District.

Rand, I respect your reluctance to put Americans in harms way by providing doctors, nurses, and mechanics to fix busted axles, technicians to deactivate booby traps, anti-tank weapons and personnel to protect them. (Anti-war liberals can support these measures.) But I wish I could dissuade you.

Maybe you are influenced by those who believe, “They are all crazies over there, so why not stay out and let them kill each other?” It is understandably confusing to sort the good guys from the bad guys.

America’s blocking aid to the Kurds embarrasses me—No, I am ashamed. CNN a few days ago reported a Kurd firing an artillery piece manufactured in 1941!…Vintage 1941!? We got to be kidding. He had 25 shells left. Any additional shells would need to come from Pakistan. In the last shipment of MRAPs (Mine Resistant Ambush Protected wheeled vehicles), Kurds got 25 out of 250!

Kurds are unequivalently Good Guys. I met the guy responsible for the well-being of 12,000 Christians. ISIS beheads Christians. Kurdish women drive cars, dress anyway they choose and serve in parliament (I think law requires they comprise 33%)

They love America, suffered their own Holocaust, and are surrounded by Persians, Arabs and Turks who are less then friendly. Sound like Israel? I have yet to meet a Kurd I didn’t like.

I share with you your angst of having an American killed there, but I feel exactly the same heartache if a Kurd is killed. As far as I am concerned, when a Kurd is killed, an American is killed.

Please change your position. Educate your libertarian followers that the Kurds are willing to be our surrogate boots on the ground. They are loyal to us and willing to confront ISIS, where everyone else in the region doesn't have the guts to do it. Where are the Jordanian and Saudi troops?

Would you support a volunteer force from our military or contractors?

I received a request from 2000 young Christian men for help in training and arming. They want to protect their vulnerable, unprotected Christian community 30 miles from ISIS. Maybe you have an idea as creative as the one you expressed at our lunch to transport all the armored personnel carriers scattered throughout small towns in America directly to Erbil. Cool idea—Hope you can make it happen. Lindsay is not interested in its being part of what he is doing, however.

Each day we delay confronting the ISIS threat we lose more of our friends, making it more difficult to destroy ISIS later. Had we reacted when Hitler went into the Sudetenland, maybe the Normandy invasion would not have happened.

You are respected by many, Rand, including myself; your leadership in engaging in the war could be historically pivotal.

God Bless,

Foster (:>)*****