I have a client who uses zoho for email.
https://www.zoho.com/mail/help/zoho-smtp.html
When you use 'Contact us' forms or 'Webforms' from a website, the Submit option is typically used to send emails. These emails are triggered from your Website Hosting Provider (Web Host). In most cases, the website's domain name matches the domain name in the email address they are sent from. Ex: www.yourdomain.com/contact.html page will submit the details to contact@yourdomain.com.
In this case, the Web Host or email server, which triggers an email, wrongly assumes that the emails should be delivered locally because the domain name is the same.
To fix this, open the WebHost settings and choose the Remote Email server option to denote that these emails should be delivered externally. You'll need to check for any Local Email Delivery configuration and switch off the WebHost's local setting. This will ensure that emails from webforms reach the Zoho Mail servers and are delivered to the correct email accounts.
In Virtualmin, how do our clients disable local email delivery and set it to an external one such as zoho?
is it just a matter of unchecking Edit Virtual Server>Enabled Features>"mail for domain" ?
Howdy - yup that's all you need to do just disable the mail for domain feature.