Before figuring out what it should say, we should ask what the goal is more specifically than "maximize impact." I expect a mass email to do very little to directly improve donations, career choices, what people believe, or how they think. So my goal for such an email would be to get students excited about the university's EA group; this seems relatively tractable.

How should we do that? I'm less sure. My college EA group recently emailed all first-year students with this goal. We included a link to get a free EA book (see here) to get students interested and for the side goal of getting EA books to interested people who otherwise wouldn't read them. We also included a brief description of EA, links to a couple relevant resources (MacAskill's TED talk, which I weakly think is the best video to get people interested in EA, and one article, which I won't mention since I'm very unsure about good intro articles), and encouraged students to apply for our Fall intro fellowship. The effect on the number of students who do the intro fellowship, by making more students aware of and interested in it, is the overwhelming source of expected value from this email.

Given I just received a link to this article in the 80,000 Hours newsletter: https://80000hours.org/make-a-difference-with-your-career/ -- that article seems like something that a lot of students might potentially be interested in. So something like a brief description of the key idea plus a link to the article would be one option.

EA UW Madison thinks of its emails as having four (sequential) goals: 

1. Let people know this org exists
2. Get interested people on the newsletter
3. Get people to come to an intro event
4. Get people to apply to the introductory fellowship

A copy of our mass email draft that we just sent out can be found here https://docs.google.com/document/d/14JQjbwWC5U8Eb82VTwozfyhrc0x_FV53n32vQuPNLas/edit?usp=sharing