Is there anything special needed to load balance SMTP with the ACE modules? Could someone please add an example?
SMTP is a TCP protocol like many others, so no special config is needed.
Make a class map to match the SMTP VIP address on port 25 (keyword 'smtp').
You can use specific probes for SMTP servers to test the application on your server.
For the return code, you can use a sniffer to see which return code you get for a successfull poll, or you can use the command "show probe detail" to see which return code you server replied with. Normally it should be 200 or 211.