Ultimately, you need to focus on delivering value and communicating this value clearly. Here are some ideas:

- write and give away an eBook related to your brand or product for users that opt-in.
- raffle a brand-aligned price or giveaway.
- create and deliver regular, useful content and invite users to opt in to be notified of new articles (content strategy).
- create and promote regular webinars where you can share knowledge and tips, in exchange for email opt-in.

You will have to continue delivering value even after you capture emails, or your list attrition will be high and engagement will be low (resulting in low deliverability).

Reach out if I can help.
https://clarity.fm/josuesierra/expertise/email-marketing-email-deliverability-best-practices