problem: email spammers for certain group

[trainer]

problem: email spammers for certain group

i have setup a sellers usergroup so we can easily identify people who are using the board to advertise products/services. no problem until recently some in this usergroup are spamming the members with ads via email. we are using the email form so is there a way to limit access to this email form for this one usergroup. i don't want them to have any access to the email form

thanks