exchange 2010

I have MS exchange 2010 configured on Site A and working fine , then I have installed Exchange 2010 on SITE B after installing SITE B I have noticed I can send E-mails from SITE A to SITE B and no issue , but When SITE B mailbox try to send E-mail to SITE A doesnt get it is sitting on the queue. SITE B Exchange cosole HuB TRansport has listed SITE A but on SITE A exhanve hub tranports hasnt listed SITE B
SITE A and SITEB are AD sites and no replication issues.
after truoble shooting I get below message from SITE B  "last error information 451.4.4.9 primary target IP address responded with 451.5.7.3 cannot achieve Exchange Server Austhentication
can some one help to fix this issue

thank you
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from server B, can you try to telnet to server A on smtp port.
CMD ->
Telnet ServerA 25

Let me know what you get.
sandyferdinandoAuthor Commented:
yes i can telnet
sandyferdinandoAuthor Commented:
if i create a reciver connector on  SITE A it works but between internal sites shouldnt need reciver connectors.
I am trying to figure out why SITE B not listed in SITE A
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You should have an internal connector port 587 and an external connector port 25 on both servers
On Site B, what do you have as send connector?
Take a look at this article:

Works the same in 2010.

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