My problem :

I have a single account on Zoho Mail with 2 users (a main user and a second one).

I have a Zoho application to send mail with zoho from my website. Depending of the user logged in my website, I want to send mail with appropriate zoho mail.

Actually the users on my website correspond to zoho users, that's simple.

So when I try to send a mail with my main zoho user through the API, it works fine. When I try to send a mail with the second user, it does not work. Zoho returns a 500 Internal Server error. But the only difference is the zoho mail fromAddress.

So my question is : how to send mail through Zoho Mail API with multiple users on a same account ? Is it possible ? Or can we only send a mail with the main user of a zoho account ?