CHAD TROUTWINE, an entrepreneur in Malibu, Calif., was negotiating a commercial lease earlier this year for a building he owns in the Midwest. Though talks began well, they soon grew rocky. The telltale sign that things had truly devolved? The sign-offs on the e-mail exchanges with his prospective tenant.

“As negotiations started to break down, the sign-offs started to get decidedly shorter and cooler,” Mr. Troutwine recalled. “In the beginning it was like, ‘I look forward to speaking with you soon’ and ‘Warmest regards,’ and by the end it was just ‘Best.’ ” The deal was eventually completed, but Mr. Troutwine still felt as if he had been snubbed.

What’s in an e-mail sign-off? A lot, apparently. Those final few words above your name are where relationships and hierarchies are established, and where what is written in the body of the message can be clarified or undermined. In the days before electronic communication, the formalities of a letter, either business or personal, were taught to every third-grader; sign-offs — from “Sincerely” to “Yours truly” to “Love” — came to mind without much effort.