Pfsense does not hates you, it's just doing what you configured See what is happening:
workstation 172.24.150.20 asks 172.24.200.254 a smtp connection
172.24.200.254 forward this request to 172.24.200.1 pool member
172.24.200.1 accepts the request and answer ok to 172.24.150.20.
172.24.150.20 rejects the message as it asked 172.24.200.254 for a connection.
Forcing source ip to 172.24.200.254 while talking to 172.24.200.1-4 using an outbound nat rule
will fix this communication issue.
You may need to change outbound nat to manual before applying the rule.