We are in the co-existence stage of our Exchange 2007 to Exchange 2010 migration and after installing and configuring Exchange 2010, we moved one mailbox form Exchange 2007 to Exchange 2010 and created a new Exchange 2010 mailbox. Our new server has multiple roles (CAS, HUB, MBX) and we added Forefront TMG 2010 to protect OWA. We use a 3rd party smart host to protect from spam and viruses. We checked send / receive connectors and DNS records and all looks good. Email traffic flows find Internal > External, External > Internal, Excahnge 2007 to Exchange 2010. It fails from Exchange 2010 > Exchange 2007.
When I send the test email from the Exchange 2010 mailbox to the Exchange 2007 mailbox, the message gets stuck in the queue on the Exchange 2010 server at hub version 8 which is SMTP relay in Active Directory Site. There is an error message for the hub version 8 queue which says:
451 4.4.0 Primary target IP address responded with: "421 4.4.2 Connection dropped due to SocketError." Attempted failover to alternate host, but that did not succeed. Either there are no alternate hosts, or delivery failed to all alternate hosts.
I seem to have the same symptoms as the one in this blog post but I am not sure where to go next.
Network Steve - Exchange 2010 and 2007 co-existence (hub transport)
Do I need to configure receive or send connectors for Exchange 2010 to Exchange 2007?
Telnet, ping, and tracert to legacy server form Exchange 2010 server are successful.
220 Ex2007server.internal.org Microsoft ESMTP MAIL Service ready at Wed, 11 Apr 20
12 15:42:41 -0600
org Hello [<IP address of Ex2010Server>]
250-X-EXPS GSSAPI NTLM
250 2.1.0 Sender OK
250 2.1.5 Recipient OK
354 Start mail input; end with <CRLF>.<CRLF>
Subject: Test from usoemail
This is a test message from Johnny
250 2.6.0 <b2734f8f-8ad5-4317-9668-4
mail for delivery
221 2.0.0 Service closing transmission channel
Thank you for your help.