I am not all that savy with mail and stumbling my way along through the intracacies of email server configuration. As some may be aware, i have been experimenting with google cloud compute instances and virtualmin (as well as a couple of other cp's).
On google cloud outbound smtp ports 25, 465, and 587 are blocked and so either one must use "GSuite" or another 3rd party mail relay host such as "Sendgrid".
Now, Sendgrid offers a free account however i believe it has a limitation of 100 emails per day...for a web hosting server with multiple clients on it, i am presupposing this would very quickly become an impossible situation for clients on my server.
bearing in mind i am using a single static external ip address and ephenumeral internal one on google cloud at present, and am offering a very basic "shared hosting service"...
Instead of me configuring webmin>servers>postfix with a single sendgrid account...can this be done at a virtualmin>virtual server level (so each one of my clients would setup their own email relay host account with sendgrid? (or competitor)