We have a paid account with two domains for example:

domain.com

and

domain.com.au

We want to use both the dot com and the .com.au emails. 

Do you:  

A: Set up 2 separate (free) zoho accounts, one for the .com and one for the.com.au, and just use each email account in a different browser/chrome instance?  (annoying, but possible).

B: Set up both domains in one (paid) account. Set up both with email hosting. Log in as different email users?

C: Set the .com.au domain is the primary domain and the .com is the alias. Use either emails from the one webmail UI.

Note: We currently have it set up as C, but we are not able to send email using the .com email address.  Mail coming in to the .com address arrives fine, but unable to send as same.

Cheers,

Juliet