HI You need SP20 /itsm008586 or tune local SMTP service as bridge between SD and other SMTP server - You Local service must allow connection without auth. but use auth. when sent email by smtp.tom.com .
I do not think this is a question of which server you are using for email, it is a question of how the machine sending mail to that server is authenticating itself. If you can cannot via telnet, then you need to authenticate using the same means you used with telnet. Otherwise, you need to reconfigure your mail server so that it does not require the authentification.
As already pointed out, OVSD is not very configurable for mail authentification until SP 20.