Hello @Doubleo,
Thank you for sharing your question with the Community.
I'm sorry to hear about the issue you are having. Unfortunately, there is nothing we can do to inherently speed up the time in which the emails are delivered. However, I have some recommendations for you to consider to optimize send time speed.
First, if possible, ensure that you set the trigger to be a list rather than a segment. Since the segment takes time to evaluate profiles who qualify, you will see longer wait times before the email dispatches for segment-triggered flows vs list-triggered flows. The following guide walks through how segments update in more detail.
Second, if you have any conditional splits (especially with complex or multiple conditions) before the first flow email, this can also slightly impact send speed since this too takes time to evaluate before filtering the user down the appropriate path of the split. You may want to consider adding these later in the flow, especially for a time-sensitive initial flow email.
Third, I encourage you to test the flow for yourself, if you have double opt-in enabled, the delay is often because users have not yet confirmed their subscription via email. Only after they confirm their subscription will they be queued-up for the flow email. If you notice the email is being dispatched promptly at testing, double-opt in speed may very well be accounting for the delay. You can disable double opt-in at any time.
If none of the above aids the situation, you may want to consider adding a static coupon code within the success message of your sign up form. That way users can use it immediately rather than waiting for a flow email containing a coupon code to arrive.
Thanks and have a great rest of your day.