With the option on the runtime pane you can stop the workflow:
for the Alert you can use the message tool from the developer palette:
Hope this helps.
Regards
@messi007 nailed it. You can also double-down on the "stop running on error" from the checkbox with the Message tool "Error - and Stop Passing Records Through This Tool" error type setting.
For this you have two option :
1- Using the event pane
2- Using the e-mail tool you can configure it inorder to pass rows with errors
For more details : https://community.alteryx.com/t5/Alteryx-Designer-Knowledge-Base/Tool-Mastery-Email/ta-p/32129
Hope this helps!
Regards,