In order to perform send mail action in a project by using already created Email Task's created template, please follow the below steps:
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2) You will be presented with similar prompt as the one below:
present elements are:
Template - please select the one from the drop-down menu list;
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Content type - Possibility to select if the email is to be sent in HTML or Plain Text format;
Send button - final step - after pressing it, mail gets sent;
Close - cancel email edition and doesn't send anything.