Hi Amanda,

There are many ways to encourage your contacts to sign up for your newsletter. You can try using one of the following methods:

• pop-up which will be displayed only to contacts with opt-out status. If you encourage them by giving them a discount code after confirming the subscription, the conversion will be more effective.

https://support.salesmanago.com/custom-modal-designer/

• personalized banners - they allow you to tailor the content from the newsletter or on your website to specific user’s interests. This content can be adjusted by the segmentation tool or the stage of the funnel where the contact belongs. The content can also be adjusted to the automation rules tool. The banner can be linked to a landing page through which contacts can sign up for the newsletter.

https://support.salesmanago.com/dynamic-banners/

There are many ways that can be tailored to your industry. Your best bet is to contact your CSM who can help you develop a strategy.
Good luck!