US law firm Morrison & Foerster (MoFo) is suing Etracks.com, a web advertising agency, for allegedly bombarding the firm with unsolicited e-mail messages.
MoFo's lawsuit, filed in February, is based on two California anti-spam statutes.
The firm is claiming that after receiving formal notice of MoFo's policy against spam, Etracks sent about 6500 unsolicited e-mail advertisements.
It claims Etracks failed to comply with a legal requirement in California that requires advertisers to include a standard warning in the subject line of messages with adult-oriented content.
The complaint also states that Etracks failed to provide a toll-free telephone number or return e-mail address to enable recipients to tell the company to stop sending spam.
In addition to a court order to stop the alleged spamming, MoFo is seeking damages including attorney fees and $50 (£35) for each e-mail delivered in alleged violation of the law, up to $25,000 (£17,000) per day.
Michael Jacobs, the MoFo lawyer in charge of the case, said: "We are a business that lives on e-mail now, so it is very important that we make the tool as productive as possible."
He added: "This spam coupled with other spam has caused a big problem."