what to add in MTA TRUSTED NETWORK

i had configured local domain (server1.tm.local) and installed zimbra. than i added some email through New External Account and gave pop address and password of that email, hence i am able to pop email of that account.

i am also able to relay emails also by logging through admin console

Global setting > MTA > Relay MTA For External Delivery
(here i gave the address through which i have to relay mails)

problem is that when i sended a test mail to yahoo i received my first test mail from zimbra but after that i am not receiving any test mails. all messages are in queue in zimbra server.
i think i had to add something in MTA Trusted Network

attaching the print screenof

Relay MTA For External Delivery
MTA TRUSTED NETWORK

plz guide what to add in MTA TRUSTED NETWORK so that zimbra start relaying emails.

Check /var/log/zimbra.log for Postfix error messages.

i sended email to yahoo and check the logs. here is the output of log

Jan 12 13:38:12 server1 postfix/smtp[15977]: C072624457D: to=<pawan_lal@yahoo.com>, relay=smtp1.mail.pw[70.87.29.134]:25, delay=61, delays=0.03/0.05/61/0.4, dsn=4.7.1, status=deferred (host smtp1.mail.pw[70.87.29.134] said: 454 4.7.1 <pawan_lal@yahoo.com>: Relay access denied (in reply to RCPT TO command))


but tell me one thing why was i able to send first test mail to yahoo ?