Mail Merge requires a Premium or Enterprise level plan.
Mail Merge is available using our legacy COM add-in within Outlook Exchange or Legacy Gmail
When you send emails with Yesware, we rely on Gmail to insert your signature for you automatically. Since Mail Merges are sent not using Gmail's default interface, a signature is not automatically included in your outbound messages.
You will need to add a signature into your Mail Merge before sending the message if you want your messages to include a signature.