Unable to send email to a contact from another user

Unable to send email to a contact from another user

We would like all our email to contacts to be sent from a house account. For example, support@example.com.

I have created a user for this account and they have a unique email address. The account has been confirmed. I have created an email template and used this email address in the from field. However, when I send an email to the contact, the mail continues to use the current user's email, not the support@example.com. It will not let me update the from address either.

Any thoughts?