You ask on APEX forum then probably you would like send mail from apex context. If Yes, you have to:
1. Configure Instance setting (INTERNAL Workspace) -> Email
2. Create plsql according APEX API http://docs.oracle.com/cd/E37097_01/doc/doc.42/e35127/apex_mail.htm#CIHDIEJI
Remember, if you will run it from out of APEX you have to set SECURITY GROUP first.
Also commit it on the end of plsql plock/procedure
3. Wait about 10 minuts for email