In the email, Musk linked to a CNBC report of a note from Goldman Sachs analyst David Tamberrino. Tamberrino said he thinks the company will report that it delivered 22,000 Model 3 midsize electric sedans in the second quarter. That is higher than Tamberrino's previous estimate of 19,000 but still below the 28,000 expected by a consensus estimate.
"“They are in for a rude awakening :)” Musk wrote in Tuesday's email, a copy of which was obtained by CNBC. The only other text in the email is a link to the CNBC story.
Tesla declined to comment.
In its first quarter letter to shareholders, Tesla said more than 450,000 people had reserved the Model 3, but the company has long struggled to meet production targets many industry watchers have said are unrealistic. At the company's annual shareholder meeting in early June, Musk said it was "quite likely" Tesla would hit its goal of making 5,000 Model 3 sedans in a single week.
Tesla had originally aimed to make 5,000 Model 3 cars per week at the end of 2017.
In his note, Tamberrino also questioned how sustainable such a production rate would be, given Tesla's history of Model 3 manufacturing volatility. To meet its goal, Tesla has added production lines at its factory in Fremont, California, including placing some equipment under a temporary tent structure. Musk also recently sent out emails to employees saying "radical improvements" are needed to meet factory targets.
However, some investors won't be that disappointed if Tesla does miss the target, for various reasons.
Baron Opportunity Fund portfolio manager Michael Lippert said Wednesday on CNBC's "Squawk Box" that his firm's outlook depends more on Tesla reaching the 5,000 per week production rate by the end of the year. He said the firm is paying more attention to the margins Tesla achieves on cars it sells rather than how many it makes.
Lippert recently toured Tesla's Fremont plant and its Gigafactory outside Sparks, Nevada, where the company makes batteries and Model 3 powertrain components. He said Tesla told him where the bottlenecks in production were in joining the vehicle's chassis with the bottom of its body.
Since touring the factory, Baron Opportunity Fund has bought more shares in Tesla, Lippert said.
Loup Ventures' Gene Munster expects the company to produce 4,300 to 4,900 Model 3s in the final week of the quarter. That would still constitute a miss on Tesla's target, but Munster does not think that's enough to change his thesis.
"I don’t think that changes the story here, which is a massive improvement, basically a doubling of production quarter-on-quarter," Munster said on CNBC's "Squawk Alley."
Tesla shares were recently flat in trading Wednesday just under $345. While shares are down about 4 percent over the past year, the stock is up about 11 percent since January. During the past year, the stock has traded as high as $389.61 in September, and as low as $244.59 in April.