There are two options in sending out messages manually.
First you would need to determine if you are wanting to use the Amazon request review button manually or send a custom email message to the buyer.
If you wish to use the Amazon request review button (the message is already created and not editable) manually please refer to this article.
If you wish to use the custom email option then please ensure you have already created a template to send out manually by referring to this article.
How to manually send out email/requests
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