Router between internet and intranet

I have Domino R6.0.2.cf1 servers. server A as internet SMTP, Server B as intranet SMTP. Server A only receive mail, and router to Server B. Server B receive/send mail for intranet users:

Server A assign internet IP: 202.106.X.X, FQDN:smtp01.acme.com.Server B assign intranet IP: 172.16.X.X, FQDN:mail.oa.com.

in firewall set router, allow Server A access Server B

the connect test is ok. can replicate names.nsf in contral panel.

then check domino address book.

Server A and Server B in same notes name networks.and in notes ports set same ports:TCPIP NetWork

test receive internet mail. error massage:No route found to server B from server A. Check Server and Connection documents in the Domino Directory.

then add connect document,smtp connect document, external SMTP network Domain.

test receive internet mail. error massage:No route found to server B from server A. Check Server and Connection documents in the Domino Directory.

why? anybody know how to solve this problem?

Subject: router between internet and intranet

Put server B in server A’s host file so server A can find server B by host name? Also, make sure firewall allows traffic on port 25 (SMTP).