If you're stopping outbound sending on a domain and want to move its DNS management away from Maildoso, the right steps depend on how you got the domain in the first place.
External domain you brought to Maildoso (BYO)
You already own this domain at your own registrar; Maildoso just manages its DNS while its nameservers point to us (see How DNS works on your Maildoso domains). To take that back:
Delete any mailboxes on the domain.
Remove the domain from your Maildoso account — contact support with the domain name (see Deleting, replacing, reducing, or cancelling mailboxes and domains).
At your registrar, change the domain's nameservers away from Maildoso's to whichever DNS provider you want to use.
Domain purchased through Maildoso
You don't hold this domain at an outside registrar, so there's nothing to point away from us — instead, the domain itself needs to move to you via a transfer-out (Dynadot push), which hands over both registration and DNS control together. See Transferring your domains out of Maildoso (push to Dynadot) for how that works and what it costs. Don't try to just "export the DNS records" while the domain is still registered through us — the domain has to actually leave Maildoso first.
Either way, mailboxes on the domain stop working once its DNS or registration moves away from Maildoso, so only do this for domains you're genuinely done sending from.
To avoid disruptions when connecting a primary domain to Maildoso, consider using a separate domain specifically for Maildoso campaigns. This ensures that changes to DNS settings for email outreach do not affect your website or everyday email services — see What are the best practices for configuring domains for Maildoso email campaigns? and How DNS works on your Maildoso domains (including websites and A/CNAME records on sending domains).
Related: Bring your own domains