In ConvertPlug version 2.2.0, we let you disable the double opt-in feature for mailers, viz. MailChimp, Mailster and Benchmark Email.
Read this article to know more.
MailPoet too allows you to disable its double opt-ins. You need not do these settings through ConvertPlug.
In order to know more about the Double Opt-ins feature of MailPoet and how to disable it, click here.