a couple of questions regarding sendmail

first of all, does anyone know why sendmail would have port 587 open in addition to the usual port 25? i see in checking my /etc/mail/sendmail.cf that it is using that as the port for the smtp daemon...shouldn't that be port 25 tho? i can't find a reference anywhere else as to why this port is open ... /etc/services only specifies port 25 as smtp.

also on the topic of mail... is there a way i can configure sendmail to reject attempts to send email by telnetting to port 25? i've seen a mailserver or two for windoze that could do this, and wondered if sendmail had a similar feature.

thanks in advance for any help you can offer. :)