What can I do when I see a [MERGE ERROR] in the subject line of my campaign?

DESCRIPTION

A merge error usually means that there are invalid merge tags or invalid tracking applied somewhere within your campaign: possibly in the HTML or Text version, in the Subject line, or in the Preheader.  Determining the cause of the error can sometimes be difficult, so it's recommended to contact Support for assistance. If you would like to look into this on your own before contacting Support, below are a few troubleshooting tasks.   

HOW-TO

a. Check your email design for invalid merges-

1. Open your draft campaign on the Campaigns Dashboard
2. Check for any merged information, like first name (searching using Control + F and searching for '%' can make that faster)
3. Verify the merge tags are correct

b. Check your content for invalid tracking-
(if you append tracking, this is uncommon for most customers)

1. Open your draft campaign on the Campaigns Dashboard
2. Check all hyperlinks created for tracking tags (%%, or [ ])

c. Check your text version for invalid merges or tracking-

1. Open your draft campaign on the Campaigns Dashboard
2. Click on the CODE tab of the drag-and-drop editor
3. Click 'View Plain Text Version'
4. Verify no invalid merges or tracking are seen