[Dovecot] problem on "multiple addresses"

I have do a search on google but found nothing.. My configuration is: RH ES3 Dovecot 1.0.0.4 from atrpms (dovecot-1.0-0_4_stable20050221.el3.at) My problem is.. my mailbox has 2 internet (interface A, ip 1.2.3.4 and interface B, 9.8.7.6) and 1 intranet (interface C, 192.168.0.x) access. Default route is on interface A. pop3/imap access from connection A & C has no problem at all. But, any connection from interface B it will get a timeout error. I can sure routing is correct.. since I have virtual host on web server and running ftp server, I tested it connecting from both IP it shows no error..

Anyone can give me some hints to fix it ?? thanks in advance.