V18 SMTP Gmail Relay - 5.7.1 Invalid credentials for relay

[Grant Moxom]

Hey Guys,
I am rolling over to V18 slowly and I have a new server with a new IP and setup my normal Gmail SMTP relay like I do in V16.
I've added the new IP to gmail's relay to allow it and everything seems to be setup correctly however when I try and send the test email I get the following.

5.7.1 Invalid credentials for relay 5.7.1 . The IP address you've registered in your G Suite SMTP Relay service 5.7.1 doesn't match domain of the account this email is being sent from. If 5.7.1 you are trying to relay mail from a domain that isn't registered 5.7.1 under your G Suite account or has empty envelope-from, you must 5.7.1 configure your mail server either to use SMTP AUTH to identify the 5.7.1 sending domain or to present one of your domain names in the HELO or 5.7.1 EHLO command. For more information, please visit 5.7.1 https://support.google.com/a/answer/6140680#invalidcred x15sm107169ljp.24 - gsmtp

Has V18 changes the SMTP procedure? My guess is that the identity sent through HELO or EHLO is no longer being sent - but anyone have any knowledge if there's something else I could try here?

 

[NickD_3CX]

Hi!

Nothing has changed that I am aware of, but you said you added your new IP right?
Did you add the IPv6 IP? Because from the message, it seems like the connection is happening over IPv6.

If you aren't interested in using IPv6, just disable it on the server where you have installed 3CX and restart all serices so that the communication happens over IPv4.