How to only send automated emails one time

[Jon]

I have an automation that occurs when an issue  is assigned and XXX field is blank. how do I set this to only send once for each issue? I have tried clicking the box that says 

"Only include issues that have changed since the last time this rule executed " 

but neigther do the trick. 

Is there a way to do this where the email will only get sent one time?

[Alex Koxaras -Relational-]

Hi @Jon 

Maybe create a manual trigger then? Or a schedule for once a year? It would be better if you could explain a bit more what you wanted to achieve.