What kind of sales person?
And do you mean the closing line (e.g., “Kind regards”), or the information provided at the very end?
Make sure to include your name, the department your work in, the name of your company, phone number, fax number (if you use it), and e-mail (it might seem kind of redundant to include your e-mail address in an e-mail, but you’d be surprised how many people can’t find it otherwise).
Other than that, I’d say it depends on what you do. Do you want people to have your cell phone number? Your office address?