Reports & Discoverer :: Error In Event Driven Report Procedure?

.I created the following procedure to implement Event Driven Reporting:

CREATE OR REPLACE procedure ABC.eve_drv_rep as
myPlist system.SRW_PARAMLIST;
myIdent system.SRW.Job_Ident;
BEGIN
myPlist := system.SRW_PARAMLIST(system.SRW_PARAMETER('',''));
system.srw.add_parameter(myPlist,'GATEWAY','apsIP/reports/rwservlet');

[code]...

Procedure is created successfully but when I execute this procedure, I get the following error:

ORA-20001'Error sending email.Error: ORA-20999
ORA-06512: at "Nml.Eve_Drv_Rep", line 17
ORA-06512: at line 1

2ndly I want to know that whether I should give IP address or Application Server Machine Name in GATEWAY parameter?
And in SERVER parameter either I should give the Application Server Machine Name or Report Server name installed on Application Server Machine?Lastly from where I can get the complete list of Parameters to be added in SRW.Add_Parameter like SERVER, GATEWAY etc.

note that we r using Database 10g Rel.2 and Forms and Reports services on Application Server and the report being called was developed in Reports 10g.