You can use the SendMail People Code function to send emails from within People Code. You can also call this function from an Application Engine.   
Note: Make sure your SMTP server is configured properly or the SendMail function will fail.

Local string &MAIL_CC, &MAIL_TO, &MAIL_BCC, &MAIL_SUBJECT, &MAIL_TITLES, &MAIL_TEXT, &MAIL_FILES, &MAIL_FROM, &REPLYTO, &SENDER;

Local number &MAIL_FLAGS;

&MAIL_FLAGS = 0;
&MAIL_TO = "email-address-message-going-to";
&MAIL_CC = "";
&MAIL_BCC = "";
&MAIL_SUBJECT = "Test email";
&MAIL_TEXT = "Sending an email from PeopleCode.";
&MAIL_FILES = "";
&MAIL_TITLES = "";

Read Further: http://sandippeoplesoft.blogspot.com/2012/11/sending-mail-through-p...