I am in the process of setting up CiviCRM to send via SparkPost using the following extension - com.cividesk.email.sparkpost
CiviMail appears to be working (both using test emails and cron) but, confirmations are not being sent when people subscribe to mailing lists or to become members.
Administer > CiviMail > CiviMail Component Settings: shows that 'Enable Double Opt-in for Profile Group(s) field' is checked.
Is there something else that needs to be done such as a scheduled job?