I have a site where visitors can send mail directly from the page.
To be able to reply I set the from header to the email adress entered by the user. While testing everything worked fine but now I encountered a problem.
If the visitor is using an gmail adress and the email gets delievered to another gmail adress, Google marks the email as potentially not from the sender. Now I went to the troubleshooting page https://support.google.com/mail/troubleshooter/2411000 and it says:
If the email wasn’t sent with Gmail, but the sender includes authentication data in the message, we’ll show you the sender’s name and the service that authenticated the message. For example, if [email protected] sent you a card from a website called ecard.com, you’d see the sender listed as “[email protected] via ecard.com.”
This is exactly what I want, but I don’t know what data I have to include in the message and I didn’t find a solution on the internet right away.
While this has no priority since everythings works and just the warning appears, I would be very glad if someone could tell me how to include the authentication data in the emails.