Mail Merge - Letters & Labels - enables you to personalise in bulk hard-copy letters to send in the post and also address labels to enable those sends.
1. Have you added the Mail contact preference to your contacts? If not you can either add that preference on individually or bulk update if they are in a group using our "Update Many" feature.
2. Have you added a valid postal address in the Primary Address fields?
3. When creating your mailmerge template, make sure that you are using and adding in the correct tags which can then be used to populate your mailmerge campaign.
If you still have further questions about this take a look at our support website and raise a support ticket to us if you have further questions.