15 April 2021
Please note that, google SMTP (or other similar SMTP server) have some restrictions in using it anywhere.
Functionality with aspmx.l.google.com
has been tested and it works properly, but the limitation in using this SMTP is that, you are allowed to send email only to gmail or G-Suit account.https://support.google.com/a/answer/176600?hl=en
If there is issues with restrictions the customer needs to be advised to check at their end to overcome this. You may advise the customer to consult with Google to further understand this restriction and act accordingly.