Strace on the qmail-remote process:

socket(PF_INET, SOCK_STREAM, IPPROTO_IP) = 3
bind(3, {sa_family=AF_INET, sin_port=htons(0), sin_addr=inet_addr("12.179.29.10")}, 16) = 0
fcntl(3, F_GETFL)                       = 0x2 (flags O_RDWR)
fcntl(3, F_SETFL, O_RDWR|O_NONBLOCK)    = 0
connect(3, {sa_family=AF_INET, sin_port=htons(25), sin_addr=inet_addr("64.12.138.120")}, 16) = -1 EINPROGRESS (Operation now in progress)
select(4, NULL, [3], NULL, {60, 0})     = 0 (Timeout)

At the same time, in another terminal: 

# telnet 64.12.138.120 25
Trying 64.12.138.120...
Connected to 64.12.138.120.
Escape character is '^]'.
220-rly-mf03.mail.aol.com ESMTP mail_relay_in-mf03.5; Wed, 06 Jun 2007 13:43:15 -0400
220-America Online (AOL) and its affiliated companies do not
220-     authorize the use of its proprietary computers and computer
220-     networks to accept, transmit, or distribute unsolicited bulk
220-     e-mail sent from the internet.  Effective immediately:  AOL
220-     may no longer accept connections from IP addresses which
220      have no reverse-DNS (PTR record) assigned.
QUIT
221 SERVICE CLOSING CHANNEL
Connection closed by foreign host.