To get more details of what "external sources" are, where, and how to configure them, please follow this article. If you wish to add external sources to your signature template, you'll learn the details (link).
Don't forget! These external sources work best with the subscription mode, which allows you to update signatures on daily basis and automatically update the external source feed.
Once you've prepared your marketing Set and Campaigns, you can start populating them. The external sources are an easy way to manage the content of your campaigns, especially when combined with rotating campaigns.
1) Start adding content from external sources by clicking on the button External sources in the menu on the left.
3) As you can see for yourself, we offer you several options how to present this content:
4) Once you choose an option and click OK, the external source placeholder will be added to your template.
Similar to other placeholders, you can design external sources placeholders to fit your signatures; changing the font to bold or italics, changing the Style (link) will be reflected in the final signature as well.