Is It Possible to Customize the Text in the Double Opt-in Confirmation Email?

Yes, you can adapt and customize the double opt-in confirmation email. 

The double opt-in email can be found under "Campaigns" --> "Automation." You can change the layout using the drag-and-drop editor. 

The most important thing is to insert a DOI link so that the recipient can complete the sign-up process. To do this, highlight your sentence – e.g., "Please click this link to confirm your subscription" – and click the link icon. For the link type, select "double opt-in link." 

Here you also have the chance to define a landing page to which the user will be redirected once they've completed the sign-up process. 

Important: For legal reasons, double opt-in emails may not contain any advertising material!