Hi @adavenue! Thanks so much for joining our Klaviyo Community. 

Regarding your first email send, I would absolutely caution you from sending your first email out to 38,140 customers. This is a very large group, and we typically tell our customers to not exceed 10,000 for the first week. Please take a look through this article, which goes into more details on warming your segment. Specifically, you should review this section of the article, which gives an overview of how to tighten up your engaged segment so that you’re not sending to a large list. 

Here’s a snippet from that article, but I do recommend taking a look through the whole guide as it’s very informative on the best strategy to ensure your have the best sender reputation
 

If your 30-day engagement segment results in a very large group of profiles, consider the following:

• Tighten the criteria of your segment
  For example, tightening a 30-day engaged segment to 14-day engagement will shrink the segment size.
• Use throttling or smart send time
  This allows you to send X amount of emails over the course of Y hours. For example, if you have 10,000 profiles in this segment, and want to send 1000 per hour, send to 10% of your segment instead of all at once, and break up sending over time.
• Take random samples of the engaged segment
  Taking random samples of your segment will allow you to send your desired amount of campaigns despite the size of your segment.

You want to be conservative in your sending during this time, and strive for as high of engagement as possible. For subsequent sends, and as long as you're getting open rates above 20%, you can create a similar segment and relax the engagement criteria to 60 or 90 days. Continue with this strategy for a couple of weeks, and then further relax your engagement criteria to 120 or 180 days.

Hope this is helpful! 
-Cass. 

Cassy,

I have decided to use Smart Send Time, and I want it to go out right away, its set for Nov 10th at 12:00am EST - so how soon will it start? at midnight tonight or within an hour of today?

@adavenue if it’s your first time using Smart Send Time, people would not get your email all at once. The purpose of Smart Send Time is to find the best time to send for your particular audience. It will start on Nov. 10 at 12am ET, and it will send every hour on the hour. Some people will get it at 12am, 1am, 2am, etc. until the full 24hours has elapsed. You can learn more about Exploratory Smart Send Times at this link. 
Thanks! 
-Cass. 
 

@adavenue Curious, how did it go?! What were your unsubscribes, open rates, click rates, order rates?