If you are using the free version of ZOHO Mail you cant use SMTP or POP3 or IMAP for your domain email, thus you will not be able to send mails from your WordPress website or store if you use a normal smtp WordPress plugin because most hosting servers require authenticated mail to be send.

To use your ZOHO Mail Free account to send mails from WordPress simply follow the instructions below to install the ZOHO Mail WordPress Plugin and integrate with your ZOHO Mail account.

The link is: https://www.zoho.com/mail/help/zohomail-plugin-for-wordpress.html