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Yes, it is possible to customize different email templates for dunning
Yes, this is possible.
Just navigate to Settings > Email Notifications (under Customer-facing essentials) > Dunning for online payments(For online payments) or Dunning for offline payments(for offline payments). On this page, you can configure the email template for each reminder for a Payment Due invoice on the panel shown in the screenshot below. You can also read this document for more information.
Note that these emails will not be sent for each dunning attempt failure. They will be sent based on the number of days the invoice has been in Payment Due state.
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