If the employer has the right to view the e-mails that were sent to the client at the place of employment, that could destroy the privilege.
Randall Ryder reports for Lawyerist.com:
"The California Court of Appeals recently found that a client’s e-mail to her attorney, regarding her plans to sue her employer, was not privileged. The court said her e-mail was the equivalent of consulting her attorney in her employer’s conference room using a loud voice and leaving the door open. Notably, this e-mail exchange occurred on the company’s servers, through the client’s work e-mail address.
In New Jersey, a court held that emails sent from a Gmail account, or another web-based account, were still private and confidential."
Read more here.