I have a task to create email reminder based on (30/60/90) days before due date from the list but I can only use OOB wf or clients side script.
NB. -No SharePoint Designer -No Visual Studio allowed ? Is that possible?
Yes that is possible. All you have to do is create a calculated column in SharePoint list that will calculate the difference of Due Date from Today and you have to make a check in your Workflow or in Client Side Script on the remaining days. Here is how you can calculate the date difference.
If you can create workflows, you can create check on the Remaining Days column if its -30/-60/-90 and then send email. I just wonder how you'll be able to create OOTB Workflows while you said you can't use SharePoint Designer.
You can also send email using general Email Sending method, SharePoint CSOM or SharePoint Rest-API. See here for more details.
Once the number is positive, it means the task is overdue.
If you want to see that remaining days in a positive number like 30/60/90 and the overdue days in minus like -30/-60/-90 , just switch the formula with below.
Hope that helps.
Nope, it is not possible.
If you cannot use SharePoint Designer or Visual Studio to create and publish a workflow to send emails before due dates, then it is not possible.
PowerShell combined with Task Scheduler would work, but then again this is not OOTB.