Action Details
Requirements and how-to articles for itch.io's action:

If you have a project for sale, you can send an email to all your buyers via itch.io.

Requirements
You need this to get it done:

Email
You can send an email to all your buyers via the Interact tab, in the email section. You can include the buyer’s purchase URL at the bottom of any email you send to make sure they can easily access any files you may have updated.
There are a couple of things to keep in mind:
Every email has an easy access unsubscribe link, avoid spamming your fans or you might lose access to them.
You can only send at most one email per day, so make sure to proof-read before sending one out.
You won’t be able to write an email before you make your first sale.
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How-To Articles
A list of useful links for you:

0
itch.io Documentation - Interacting with your fans
Information and tips regarding interacting with fans on itch.io.
Official
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