After you've created the first version of your email, clone it four additional times and include which day of the week the email should be associated with.  In the below example, <Email Name> would be the name of the email.

Navigate to workflows by clicking on "Automation" --> "Workflows".  Create a new workflow and name it "<Email Name> - Peak Engagement Day Test" where <Email Name> is the same used in the prior step.  Next, select "Start from scratch" in the top left and choose "Specific Date" as how you want the workflow to start.

The date and time you select would be the cutoff point where any new members of an active list would not be enrolled.  For example, if you say the cutoff point is at 8:00am on Monday and a contact becomes a member of the active list at 8:05am on that Monday, they would not be included in the mailing.

You'll now want to select the active or static list(s) that you want to send the email to for this test.  Click inside the "Contact enrollment trigger" step --> 
Click on "List memberships" --> Select the list(s) you want to send the email to.  In the example below, we're selecting the list that is called "100K List" --> Click "Apply filter" --> Click "Save"

You'll now want to select the active or static list(s) that you want to send the email to for this test.  Click inside the "Contact enrollment trigger" step.

Choose the triggers that decide how a contact enters this workflow.
Set up triggers

Select the list(s) you want to send the email to.  In the example below, we're selecting the list that is called "100K List".

Underneath the delay (which is the cutoff point for any new members of the starting list(s) being able to start the workflow), click on the "+" symbol to add a workflow action step.

Search for "split test automation" and click on "(Beta) Five cohort split test automation"

Underneath the split test automation step, click the "+" sign to add another workflow action step.

Select the "Value equals branch" and click on this --> Click "Choose a property" --> Click "Five cohort split test automation" --> Click "cohort" --> Click the checkbox for "Create a separate branch for each value in this property" --> Click "Next" --> Click "Save"

Select the "Value equals branch" and click on this.

Click "2. (Beta) Five cohort split test automation"

2. (Beta) Five cohort split test automation

Click the checkbox for "Create a separate branch for each value in this property".

This will automatically create 5 cohorts where each cohort will represent a day of the week.  For example, Cohort A = Monday, Cohort B = Tuesday, etc.  For each branch, you'll rinse and repeat the following steps.  Click on the "+" sign to add an action step underneath "Cohort A".

Next select the day that corresponds to the day of week you want to test.  For example, for Cohort A, you'll want to select the corresponding date that is the Monday.  Next select the time you want to send your email on that day.

We recommend that you send your email(s) at the same time across the week as to not create another variable in your test.

You should never see contacts flow down the none met step, however, If you want to take a belt and suspenders approach, you can treat this branch as a default branch.  What we recommend doing here is to clone everything under the "Cohort A" branch and place it here.

Underneath each "Delay" in each cohort, you'll want to add a "Send email" action step.  You'll click the "+" sign.

Select the email that corresponds to each cohort.  For example, "Cohort A" would be the Monday email, "Cohort B" would be the Tuesday email and so on.  You'll repeat this step for each cohort.

Once the structure is set, click on "Review and publish".

You'll then select "Yes, enroll existing contacts who meet the starting criteria".  For any new contacts that meet the starting criteria, they will automatically be added up until the cutoff day / time.

You can then compare the success of how each day performed using the "Compare emails" function on the marketing email performance screen.

Finding your peak email engagement day of the week with HubSpot