My domain and email hosting is Ionos, I'd like to switch to ZOHO, I purchased 1 user to do the test, I don't know how to set up.  I have the following issue:

1. I tried to only transfer 1 mail account to test, once I set up as the suggestion, all other email under the domain hosting doesn't work. 

2. After I set up, I tried to send email out, and receive the test email, it doesn't work. 

3. I thought because the email account still under ionos, so I deleted my account, made me mass on that moment, I still can not receive and send email

I have to reset my domain DNS, if you have sales person who can set up everything for me it will be perfect.