Doctors reported that the woman went to bed about 10 p.m. but got up two hours later and walked to her computer in the next room, Britain's Daily Mail newspaper reports.
She turned it on, connected to the Internet, and logged on before composing and sending three e-mails. Each was in a random mix of upper and lower cases, not well-formatted and written in strange language, the researchers said.
One read: "Come tomorrow and sort this hell hole out. Dinner and drinks, 4 p.m., Bring wine and caviar only."
Another said simply, "What the ..."
The new variation of sleepwalking has been described as "zzz-mailing."
"We believe writing an e-mail after turning the computer on, connecting to the Internet and remembering the password displayed by our patient is novel," the researchers said.
"To our knowledge, this type of complex behavior requiring coordinated movements has not been reported before in sleepwalking," they wrote.
The neurologists said that unlike simple sleepwalking, the activities their patient was involved in required complex behavior and coordinated movements including typing, composing and writing the messages.