How to properly delegate a domain to Yandex?

Question

DigitalOcean

I delegate the domain (in digital ocean) to Yandex to create corporate mail.
Question:
Should I delete all previous NS and leave only new Yandex? How will this affect the operation of the site (deleting the old NS - I am attaching a screenshot of the old NS)?

Answer 1

You don't need to delete ns, just add dkim, spf, and mx and you're done.

Answer 2

Mail will stop coming to old servers and will come to new ones. Accordingly, clients will also need to be reconfigured to new servers without losing the latest emails from old servers, that's all.