I found out that Gravity Forms does not send emails form the ‘from’ address, but it uses the php mailer adress instead. That is the account address in DirectAdmin. One has to activate WP Mail SMTP next to this plugin and add settings there for the send address and password. Otherwise the account login credentials are revealed on the internet and mail header. That is not what one wants.
So please integrate the smtp login, or make an explecit announcement that the use of a second pluging is needed (WP Mail SMTP or perhaps SMPT Mailer).
We found out this with a client that uses default MX to Microsoft, but would send email from our server as a result of a contact form without the need to create an extra account on MS. The reply addres is set to the default MS address of cource.
We have set SPF and DKIM records that allow sending from our server, and also SSL certificates to allow STARTTLS.
When Gravity SMTP is used without configuring a specific integration or when using the PHP Mail integration, then messages are handled by the server (as if the the plugin weren’t installed) and the plugin acts only as a logger. When one of the Integrations is configured it will handle all properties of the message without need for another plugin. If you’re encountering issues with this, please open a support ticket and we can help troubleshoot.
And I could have seen that behavior because Gravity is not asking to configure the SMTP login and passord. So it relies on php-mail. Please add SMPT to the options.