Emailing a list of users when a record is entered in the database. - Mailing list pgsql-novice

Hi,

I need to develop my database so when a record is entered through a
browser, it will automatically email a list of interested parties. I
am ok at designing the tables so the relevant personid's have the
email address and their interested subjects. But can anybody help on
how to email the parties when the data is passed.

The only knowledge i have on this is the command

"cat {filename} | mail {emailadd} -s {subject}

Thanks in advance for any help