RE: Reminder E-Mail for workflow
In Approval Entries, there is a field named - Approval Due Date, which get its value when approval is requested (default 0D).
If you would like to change that you can change the workflow page to define a Due Date Formula in first response section. (Where you define type of Approver Type).
To Send Overdue Email there is a base report 1509 "Send Overdue Appr. Notif."
Run this report and system will send overdue emails. If you want to do it in schedule you can configure this report via Job Queue.
Hope that answers your question.
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