I am in Zoho Mail and the default IMAP shows Zoho Mail imap.zoho.com.au and the out is smtp.zoho.com.au

This is the default IMAP. I can't recall how this was set up.

I want to change this to gmail as I am using GSuite and before I migrate fully to Mail I would like to try it out with the GMail IMAP.

How do I change the Default setting?

I've tried adding another email (same email address as the Default) but it fails the Gmail IMAP Authentication. I checked the Password and settings (twice) and they are correct.

How do I reset the default? I doesn't allow edits.

Any assistance would be appreciated.