How to setup smtp address for Enterprise Manager 10g

Hi, Let say my company has smtp server, with the ip of 1.2.3.4 and name of smtp.mycompany.com

from the db server:

telnet of 1.2.3.4 25 is successful.

telnet smtp.mycompany.com failed.

so someone try to insert this info into the /etc/hosts where 1.2.3.4 is smtp.mycompany.com.

now telnet smtp.mycompany.com 25 is successful because smtp.mycompany.com is equal to 1.2.3.4

however when i use this smtp.mycompany.com as smtp address inside Enterprise Manager to send alert e-mail, I'm getting this error:

"Test Failed With Messages: Illegal address"

How do I actually setup smtp address for Enterprise Manager to send alert?