Looks like Google made some changes in April 2020 that requires stricter TLS Authentication. Now getting this message when trying to "Send mail as" from an account setup in ISPConfig. (Also attached the actual image on this post) Code: The response was: TLS Negotiation failed, the certificate doesn't match the host. I went to setup the user again, which was setup on port 587 with my domain as SMTP server and my email as the username previous, but now when I try to save the setup I get Authentication failed. And the error is : Code: "TLS Negotiation failed, the certificate doesn't match the host., code: 0" Looks like it's VERY common problem on the internet with all Panels, like Plesk, Cpanel, etc all having issues. I'm surprised this hasn't come up here yet to be honest. I only found one link and it was in the priority forums, so was not able to reply. However, does anyone know a fix to this? When I try to add the user on the "send mail as" in google, the settings I use worked before, but not any longer, and they were : SMTP Server : mydomain.com User : [email protected] Password : mypassword ( which I know is correct as I changed it to make sure) Port : 587 (And also tried 465, which I did also open up in the firewall) Secure Connection Using : TLS (But I tried SSL also) What DOES work is using no encryption and port 25, but I don't want to do that. Can someone else give this a try with a email account setup in Ispconfig? I'm not sure how to fix, but I think it may be a common issue now. By the way I did setup the SSL cert for both ISPConfig and symlinked it to postfix. As I said, this worked previously for me using TLS on Port 587, but looks like Googles stricter policy needs domain to match domain on cert, which from everything I can see it does. I even tested on https://www.sslshopper.com/ssl-checker.html and domain matches the cert. I'm so lost.. Thanks so much.