Hi Mario,

how can I send an email when a user renew its plan?

Since the subscription status do not change during renewal, the only way you can trigger to send emails is by using the 'Invoice Paid' status(http://take.ms/eYrS4).

This way, after the user successfully paid their renewal subscription fee, the email will be sent.

PS: This also mean that the email will be sent when user pay for plan activation or in other words, when an invoice is paid.