Monitoring custom page on SMTP server

You can assign a standard http monitor to the pool. By default a pool monitor will monitor the ports listed per pool member. However in the monitor configuration you can override this and specify the port that you want.

For example: If the server team wants to bind an HTTP server to port 80 on the SMTP server, you can assign a custom http monitor that inherits (defaults-from) the built-in http monitor, and change the destination to _:80. (_:80 = probe the ip of the pool member, but on port 80 instead of port defined by pool member)

Works the same for HTTP or HTTPS monitors, and you can set your SEND and RECEIVE strings as normal. Set the SEND string to get the file, and RECEIVE string to an appropriate value that will be in the file. You can also set a Receive Disable string so the file can be modified to disable the pool member as well.

[Edited to add] Check Cory's answer here for an example. Just leave the address portion of destination as the wildcard * to monitor all pool member IPs.

Also noting: GUI lists these as "alias address" and "alias service port", while TMSH combines these into the "destination" field.