Yes, you are allowed to add custom fields to your email subject lines, just make sure that you add proper place holders like [FIRST_NAME] in the email subject lines and it will be replaced after you send email newsletters.

Custom fields, you might have heard this word in your senders account. Have you ever wonder what is the use of this? Or why does it have been included in the features? Collecting your subscribers email address and getting permission from them to send campaigns to their inboxes is the most essential part in email marketing. But after this, what if you want to personalize your messages. Personalization is the key factor to get engaged with your subscribers in the very best way. There comes the pa...