That said, with double opt-in enabled, Forms API submissions will trigger the opt-in email to send. Depending on your use case, this could be used as an indirect way to send the emails.
Other alternatives include:
Manually sending the opt-in email on an individual contact record, per this article.
Subscribing contacts who have consented through your custom form to specific email types through this Email API method. (Keep in mind, this is different than using double opt-in. Work with your legal counsel to determine whether you could comply with local privacy laws through this method.)
That said, with double opt-in enabled, Forms API submissions will trigger the opt-in email to send. Depending on your use case, this could be used as an indirect way to send the emails.
Other alternatives include:
Manually sending the opt-in email on an individual contact record, per this article.
Subscribing contacts who have consented through your custom form to specific email types through this Email API method. (Keep in mind, this is different than using double opt-in. Work with your legal counsel to determine whether you could comply with local privacy laws through this method.)