I have no idea why Godaddy have to make things difficult by trying to be simple (different).

1. Whenever the main domain needs to be referred @ is needed and a must. I had used “domian.com.” but it didn’t work – the DNS records were not propagating
2. Where there is a subdomain, the domain should not be a part of the Host Entry – that is a must. For example – “mail.domain.com.” should be written as “mail” only.
3. Similarly when referring to the main domain @ is needed
4. For reference below are some examples

a 	@ 	17x.xxx.xxx.xx5
a 	mail 	17x.xxx.xxx.xx5
cname 	www 	@
mx 	@ 	mail.gxxxxxxxxxxxxxl.com (Priority: 10)
txt 	@ 	v=spf1 mx a ~all
txt 	_dmarc 	v=DMARC1; p=quarantine  # the quarantine or reject is needed.
txt 	default._domainkey 	v=DKIM1; t=s; p=MIxxxxxxxxxxxxw0xxQE

It needs the name of two nameservers with the same domain name for setting custom Nameservers.