I am taking steps in the manual to set the automatic mailing but I cannot find this setting mentioned in the manual.

Question

Now please open the opt-in question again for editing. Under Additional settings, tab Confirmation select under Forward after confirmation → Questionnaire link off now please select the serial mail 1. It is convenient that you enter no text for confirmation (text at confirmation) in the opt-in question, then respondents will be redirected directly to questionnaire A2 (what serial mail 1 refers to) after confirmation. Save this setting (Save question).