Hello!
Options for notifications, like the Email Reports package for gateway events and script support, have been discussed here :
https://forum.netgate.com/topic/155063/notification-on-events?_=1600390142279
My understanding is that pfsense is not an mta, and while is has its own form of "queueing", it will not send notifications if it cannot reach your smtp relay.
My preference is to setup a pi along side pfsense as a support server to run things like an mta (postfix, exim, ...), local monitoring (nagios, icinga, ...), and other things that I dont want to burden pfsense with even though it might be able to handle them (squid, nmap, ...). YMMV.
John