If you are sending an email such as a welcome email to a new subscriber right away in your campaigns and automations, we recommend inserting a 20-minute delay before doing so while using our Superfloss feature. If it's not ideal to do 20 minutes, then try 10 minutes, and if that's too much, try 5 minutes, etc. The longer the delay the better to ensure the email address gets verified and dealt with if it is invalid, preventing the bounce. It is not recommended to not insert any delay, as it will be impossible to know if the welcome email automation runs first or Superfloss does.
The recommended 20-minute delay will cover most of the Superfloss email verifications but some might take longer. This depends on many factors like how long of a delay before the email address is sent to us from our partner integration, how busy our load is, the type of email address we are verifying, etc. We are continually improving our Superfloss speeds and expect only to improve over time.