In some contexts, the first line is treated as the subject of an email and the rest of the text as the body. The blank line separating the summary from the body is critical (unless you omit the body ...

"His fiancé was great, she said, 'I'll buy your dinner if you put him on Team USA!'" "All right, you're buying," Guerin said. "Because he's in." As Guerin relayed the moment -- which was followed ...