Shares of the company were up more than 1 percent in early trading Friday. The stock is down more than 11 percent this year as Starbucks struggles to recover from weak same-store sales and poor foot traffic.
In the most recent quarter, Starbucks topped same-store sales expectations, but traffic remained flat. The beat had been viewed positively because it followed five straight quarters of misses.
"The stock (which in almost 40 years) I have rarely commented on is cheap and undervalued," Schultz said in an email to CNBC's Jim Cramer.
The coffee giant has been working on a number of initiatives to turn around these weak sales, including offering more cold beverages, revamping its rewards program and increasing its marketing efforts to non-Starbucks card holders. The company expects these new digital efforts to contribute 1 to 2 percent to same-store sales in the Americas in 2019.
"Given Starbucks scale and global footprint it's almost inevitable that we will face cyclical changes in the business," Schultz said in the email. "Some self-induced (after all we're all human) and others due to market forces. Yet, if you look at our history (26 years) as a public company we have always been a learning organization that is built on a foundation of growth and innovation, leading to superior financial performance. I can unequivocally promise you this time will be no different."
"And, for those who have looked at Starbucks whenever there has been a glitch in US comp store sales, and determined the glass is half empty they are respectfully dead wrong," he said. "With regard to China, it's going to be bigger and more robust than the US ever was, full stop."
Schultz joined Starbucks in 1982 as director of operations and marketing. He led Starbucks' expansion from a single coffee shop that opened in Seattle's Pike Place Market in 1971 into a global giant with more than 28,000 locations.
"Kevin [Johnson, CEO] with Roz [Brewer, the chief operating officer] and our leadership team will lead us to the promised land," Schultz said. "We have built a great and enduring company. And, as my mother was so fond of saying, 'this too shall pass.'"