Cisco ASA 5505 Static Assignment Issue

I've been fighting with a Cisco ASA 5505 for the past couple of days trying to pass traffic on a site-to-site VPN. One of my Google searches hit on this blog entry. This entry is a note to myself to remember (which I probably won't) that if you use a Cisco ASA 5505 with only a single outside IP address, ensure that you use the interface keyword when creating static routing entries. For example, the following entry will not work:

static (inside,outside) tcp 12.34.56.233 smtp 192.168.1.188 smtp netmask 255.255.255.255

The following entry, however, will work:

static (inside,outside) tcp interface smtp 192.168.1.188 smtp netmask 255.255.255.255

I'm familiar and comfortable with several Cisco routers and switches, but I have to admit that the ASA 5505 is one of the most confounding network products I've had the opportunity to use. That being said, I would not consider using networking hardware from anyone except Cisco.