mail queue problem

I have created a website which sends out automated emails to users subscribed to the website using the mail_queue package. The mails that these users receive are not intended to be replied to so the email address should not be displayed in the email. However, every time I try to set the $from variable to some name like "system administrator" the mail fails to send. If I set $from to empty it also fails to send. Is there any way I can stop the email address from showing up in an email and replacing it with just some generic name instead. In theory for a mail to be sent successfully all you need to provide is a correct recipient address anyway. Any help would be appreciated, thanks!