We use Zoho campaigns to manage lists, and have embedded signup forms in various web properties we manage.

When someone signs up by entering their email into the form, they receive an opt-in confirmation email.

However, this email always ends up in their spam box. Furthermore, the email appears to be sent by zcsend.net instead of from us.

We've already set up DKIM and SPF on Zoho and have verified that it works properly with our campaign emails.

How can we fix the opt-in confirmation email so that it behaves like the rest of our emails, so that it no longer always goes into spam?