Setting up Email Groups

Setting up Email Groups

I have a number of email accounts with different domain names linked to my Zoho Account and wish to set up a PUBLIC EMAIL GROUP for one of my email accounts ie ENTRANTS@DOMAINNAME2.COM but I cannot do this as it is forcing me to do it as

ENTRANTS@THEMAINDOMAINNAMEONZOHOACCOUNT.COM

How can I get it to allow me to do it for one of the other domain names I have an email account for ?