irule to send email alert when a node is marked down by health monitor

you don't normally do that with a iRule, they are meant to do things for the traffic that goes through a virtual server.

this knowledge article explains how to achieve what you want: https://support.f5.com/csp/article/K59616664

thanks Boneyard for your reply.

i did look at this article, But i want to apply this to a single node or couple of nodes. not sure how to modify that command.