Hi,
I would create a timer to do that.
you can set up the timer to run whenever you want
and you just need to care about the logic to get the users emails and send that email

EDIT:
Please check https://www.outsystems.com/forums/discussion/6905/overview-of-the-email-capabilities-of-the-outsystems-platform/ to have an overview of the emails capability of the Outsystems Platform

Best Regards

Carlos Rocha

@carlos Thanks for your reply 

in my data i have a field called expiry date. by using this field i want genarate emails to the user
like your expiry date is in 30 days.

Exactly if the user expiry date is in next 30 days then the particular user and admin has to receive an email notification about expiry date.

so you just need to run the timer once a day and check if that expiry date is 30 days away and if it is you send the emails.

you can use the condition DiffDays(currdate(),expiryDate) = 30 to verify if you need to send the email or not 

Best Regards

@carlos thanks for the reply.

can you please help me out with some tutorials to implement such functionalities.