Personalized Subject Line

This guide will help you understand

  • What is a personalized subject line
  • Why you should use a personalized subject line
  • How to create one in Bloomreach Engagement

What is a personalized subject line

Bloomreach Engagement enables you to easily design personalized subject lines to increase customer engagement. Emails can be personalized using various customer/event attributes or price related information.

To test the impact of subject line personalization, it is advised to create a scenario with multiple subject line variants and test them against the control group, as will be shown in this guide.

Why you should use a personalized subject line

Information overload and generic emailing are causing a decline in email open rates. Now, more than ever before, we are being bombarded by an unprecedented number of marketing emails on a daily basis. As a result, your customers have negative connotations when seeing email subjects containing phrases like “sales”, “limited offer inside". All these phrases are being unconsciously filtered in customer minds when going through their email inboxes. Such behavior is negatively influencing, not only email open rates, but also other related metrics like click-through rate, conversion rate and revenue per visitor.

Subject line is the first bit of information customers see when scrolling through their inboxes . No matter how good the content is inside, if the subject line does not immediately catch the attention of your potential customers, the email will fall into oblivion, or trash. To increase email engagement, businesses need to find new creative ways how to approach customers in a way that is highly personalized and free of overused marketing phrases and tricks.

How to create one in Bloomreach Engagement

Step 1
Visual Editor: click on the {} symbol located in the bottom part of the editor.


HTML Editor: click on the + symbol located in the bottom part of the editor.


Step 2
Visual/HTML Editor: use the drop-down menu to select the desired information and copy and paste the generated Jinja code to the subject line.


Note: If a customer is missing the selected attribute, nothing will be returned.
E.g. Hello {{customer.first_name}}, how are you?
If the first_name attribute is not available for the recipient of the email campaign, the subject line will look like this: Hello  , how are you?

Use case versions 

Using customer attributes (first_name or last_name)

  • Easiest approach to personalization.
  • Customers are usually used to this practice = may decrease the efficiency of this technique.

 Jinja code

{{customer.first_name}}, these are the deals that might interest you.

Using trigger event attributes

  • Personalization based on the triggering event.

Example Customer purchased a new shirt and you would like to inform him/her about the shipment details via email. The triggering event in this case is purchase.

Jinja code

Your order {{event.purchase_id}} is on its way!

Any trigger event attribute can be accessed using this logic.

Using product information

This might be used for:

  • Including product information to the subject line.
  • Improving performance of other campaigns (abandoned cart).

Customer has left a product in her shopping cart. To improve the performance of the abandoned cart email, you can fine-tune the subject line with the name of the product left in the cart.

Jinja code

Don't forget you still have {% set firstitem = event.items[0] %}{% item = catalogs.catalog_name_here.item_by_id('firstitem.item_id') %}{{item.item_name}} in your cart!


Using this Jinja code assumes triggering  the scenario by a cart_update event, which has items tracked as specified in the abandoned cart email guide.

Using discount information

This can be used for including the exact amount of the discount in the subject line, which is more effective than using a percentage discount.

Using the Jinja code below, you can create a personalized subject line showing a 10% discount from the specific amount as an exact amount.

Jinja code

Do you want £{{ '%0.2f' | format(event.total_price  * 0.1) }} off your pending order?

There are many other ways of how you could personalize subject lines. You will easily achieve the desired personalization using the editor wizard and Jinja. You can check out our guide to Jinja.

Testing and Evaluation

Once the personalized subject line is ready, it is advised to test it against the control group using Bloomreach Engagement A/B test functionality in the scenario builder. Following this approach, you can determine the impact of the personalized subject line.


The result of a successful email campaign with a personalized subject line should be an increase in the open rate and other associated metrics (RPV and click-through-rate).


  • If you see an uplift in other metrics while open rate is remaining static, you should always double check  the accuracy of the report, since the increase in other metrics should always go hand in hand with the uplift in open rate.
  • When designing your segmentation, pay attention to the fact that the actual subject line is not tracked anywhere. That's why we recommend naming the complete email node (tracked in campaign.action_name) with the same text as in the subject line. This will enable you to have a better overview of the results.
    For example in the scenario above Purchase confirmation Subject 1 should be renamed to Purchase confirmation "text of the subject line”.

Your evaluation can look like this: