OWT does not allow it's users to send unsolicited commercial Email (UCE - also known as "spam"). The use of OWT mail servers to send unsolicited commercial Email is strictly prohibited and a violation of this policy could result in the termination of access services.
The spam problem is immense and many of the larger providers (Yahoo, MSN and AOL and others) tend to take a hostile stance on this. If even a SINGLE OWT user's account were to be compromised, or their computer were to get a virus/worm/trojan and send out even a fairly small amount of UCE messages that provider may ban the OWT mail server temporarily or indefinitely. For this reason we must be tough on UCE and even place some restrictions on legitimate bulk Emailing.
Our mail servers will recognize Emails to a large number of recipients and should your account send to large groups of recipients (over 15) 4 or more times in a 15 minute period of time your account may be suspended until we can contact you. If you have a large group to Email for legitimate reasons the solutions is to just break this up over time so that you do not send 4 Emails to 15 or more recipients in any 15 minute period. We apologize for this inconvenience but since these large providers refuse to deal with spam in an intelligent manner we are forced to do this to avoid blacklisting.