Send an email to the current assignee only if the priority is set to "Highest" or "High".
Configuration
Add the Send email post function to the desired workflow transition or create a new transition.
From
Choose the option User in field with the value "Current user" (this is the default value).
To
Select Field containing users and select the field Assignee.
Email content
Subject
Select the parser mode General and enter
%{issue.key} - Action required
Email format
Choose HTML
Body
Select the parser mode General and enter the following expression:
Hi %{issue.assignee.displayName},
this issue needs your attention. Please provide feedback as soon as possible!
Thanks,
%{system.currentUser.displayName}
Conditional execution
Select the parser mode Logical and insert the following expression: