Personalising your subject line

A subject line that speaks directly to the person receiving it consistently outperforms a generic one. Personalisation signals relevance before the email is even opened, and relevance is what drives open rates. Here is how to use it effectively in Flexmail.

Before you start

Personalisation based on empty or incomplete data creates broken or awkward subject lines. Before adding a placeholder to your subject line, check three things:

• You have the relevant contact data stored in a custom field, such as first name, city, product, or account details.
• Your contact data is reasonably complete for the segment you are sending to.
• You know what the fallback looks like when a field is empty for a contact. Test this before sending.

Using the contact's name

Adding a first name to the subject line is the most common form of personalisation. "Sophie, your order is ready" or "Hi Marc, here is your monthly summary" create an immediate sense that the email was written for that specific person.

In Flexmail, add the #firstname# placeholder to your subject line. Before you send, check what happens when the field is empty. If a contact does not have a first name stored, the placeholder is replaced with nothing, which can result in "Hi , here is your summary". Send a test to a contact profile with an incomplete name field so you know what your fallback looks like.

Using location

Location-based subject lines can outperform name personalisation in some contexts. "Top restaurants in Ghent this weekend" or "Events near Leuven" make the email feel local and immediately relevant, especially for event-driven or location-specific content. Store location data in a custom field and use the corresponding placeholder in your subject line.

Using product or account data

For customers, referencing the specific product they use or subscribed to creates strong recognition. "Your subscription renews in 7 days" or "New accessories for your [car model]" work because they reference something the contact already has a relationship with. This requires storing the relevant data in custom fields on the contact record, populated via import or API.

Keeping personalisation meaningful

Personalisation only lands well when it feels genuine. A subject line that opens with a contact's name and then delivers completely generic content creates a mismatch that undermines trust. The personalisation should connect to the email's content. If you mention a contact's city in the subject line, the email itself should contain something relevant to that city.

Common mistakes to avoid

• Not testing the empty field fallback before sending. Always send a test to a contact with missing field data so you can see the broken version before your full audience does.
• Using name personalisation in every email regardless of context. If every email starts with the contact's name, it stops feeling personal and starts feeling like a template.
• Personalising the subject line but delivering generic content inside. The subject line sets an expectation. If the email content does not match it, contacts feel misled.
• Using a field that is only partially populated. If only 40% of your contacts have a location field filled in, a location-based subject line will look broken for the other 60%.

Next steps

• Check your contact data completeness before using a placeholder. Go to Contacts and filter for contacts where the relevant field is empty.
• Run an AB test on your next campaign: personalised subject line versus non-personalised, with the same offer.
• See "What makes a good subject line?" for broader subject line guidance.