Wrong SNMP Trap email alert being triggered in user_alert.conf

I don't think you've provided the actual config that you used, because the example above would generate a syntax error due to the spaces in the name "WEBPAGE1 Monitor Fail"

alert WEBPAGE1 Monitor Fail " SNMP_TRAP: Pool ....

So I'll assume you haven't actually made that error on your real device (if you have, you'll see alertd restarting constantly, and messages about an error on line 1 of /config/user_alert.conf in the /var/log/ltm log)

From the text of the error message you're matching on, it appears to be a GTM alert that you want to act on.

I've set up a quick test, and for me, it appears to work (it sends the .201 and .202 traps, though I could just have easily set it up to send email, as you have done)

Here's what I've got in alert.conf:

alert WEBPAGE1 "SNMP_TRAP: Pool /Common/gtm-pool member /Common/test1 .* state change" {
   snmptrap OID=".1.3.6.1.4.1.3375.2.4.0.201;
}

alert WEBPAGE1 "SNMP_TRAP: Pool /Common/gtm-pool member /Common/test2 .* state change" {
   snmptrap OID=".1.3.6.1.4.1.3375.2.4.0.202;
}

Then I have a GTM pool with two virtuals in it, and I'm bring those virtuals up and down to generate the messages. When that happens, I get the normal snmp trap for that message, plus the .201 (or .202) OID.

If you're wanting to monitor the LTM event, then you would need to change the match pattern to the appropriate ltm log entry.