If you change your domain nameservers does that void all DNS/MX/A record you input in your domain registrar?

Question

say you have a domain (mydomain.com) in registered to a registrar, say namecheap,

you have setup MX record to handle email sent to your domain

you h

Answer 1

In somewhat laymen's terms:

You need to distinguish between 3 different (yet related) services:

1. Domain name registration - you pay for your domain name here. Except for the name itself, here you need to enter your Domain Name server names, which will point to where the next service is hosted:
2. DNS service - here is where you enter all your records (A, MX, ...) which point to your other services (web hosting, mail servers, etc..)
3. Service hosting provider (for example web hosting, or email service)

You can have different parties host these services for you, but it is not uncommon that one service provider can offer all these services. From your description, it looks like that at the moment your Name registrar (1) is also hosting your DNS service (2) (which is quite common). Now, your new web hosting provider wants to host your DNS service, and is requiring that at your name registrar, you enter its name server names (which is also not uncommon). And you are right, if you do that, any DNS records that you entered at your current DNS provider will be void (they will remain there, but no end user will ever see them since (1) will point them to use your new hosting provider's name service to resolve your domain records).

You have two options:

1. Do not comply with your webhost's request, instead ask them what DNS records (probably A or CNAME) you need to add at your current DNS service provider in order that your new website becomes reachable.
2. Comply with your webhost's request, but then you will have to go to your new provider's name service console and again add all the records that you already have entered at your previous DNS provider.

I would choose option 1, as less risky