Hello,
please use the hoststatus command on the CLI to check what the problem could be:
CLI: hoststatus lasllc.net
Check if the host shows up or down, and if there are any errors at the end of the output. Also hoststatus gives you the destination IP(s) the IronPort tries to connect to, if they are not reachable for some reason, the appliance will keep attempting to send messages to that domain until delivery expires, in your case 3 days. This is set by your bounceconfig.
Hope that helps,
Andreas
PS: A uselful command to check connectivity is
CLI: diagnostic->network->smtpping
Use that to check the IPs given by the hoststatus command.