Okay,   we were checking for from address but you mentioned that assignment should be on basis of To Address. Following code should work.

1. // Define Caller Details
2. var callerID = gs.getUser().getRecord();
3. var sEmailAddress = email.direct.toLowerCase();
4.   if (sEmailAddress.indexOf("ithelpdesk@conns.com") != -1) {
5.   current.assignment_group.setDisplayValue("IT Helpdesk");
6.   }
7. else if(sEmailAddress.indexOf("security@conns.com") != -1){
8. current.assignment_group.setDisplayValue("IT Securities");
9. }
11. current.caller_id = callerID.getValue('sys_id');
12. current.location = callerID.getValue('location');
13. current.u_phone_number = callerID.getValue('phone');
14. current.contact_type = 'email';
15.  
16. // Define Incident Details
17. current.status = 1;
18. current.short_description = email.subject;
19. current.description = email.body_text;
21. current.insert();