Ok, this is a confusing topic because there are two distinct things you could mean by this. The first is if you want rich@foo.com to actually go to rich.tong@foo.com. And the second is if you want hr@foo.com to actually go to a group of people in the company like rich@foo.com and tony@foo.com.

The confusing thing is that the mechanisms for doing this are very different:

1. For what are called mail alias, you go to https://gsuite.com and login, then go to Users and then click on the name of the user. The confusing thing is that there is nothing on that pane that tells you anything, so click on User Information at the downward arrow on the right or there is in small type User Details. If you scroll down you will see Email aliases and again no apparent user interface, but if you click on it, a pen icon comes up and you can edit there. So four levels deep is where you can make rich.tong@foo.com, richt@foo.com so forth point to the same person.
2. If you want an external alias (what they call a mailing list) to work, then you are actually going to create a Google Group. This is confusing because they are overloading the mechanism for discussions to make a mailing list. So go to Groups and then Create group at the top. The confusing thing here is that everyone who is in the group will also get email everytime a new post ends up there, but the group is *not* visible to the Internet. So this is a good secure mechanism, but you have to do extra work to make it visible.
3. To create an external mailing list work, you need to splunk permissions of the group when it is created. There is at the very bottom a checkbox for External and Publish Posts and this gives you want. It's confusing because I don't think of publishing posts as emailing to a email alias. You will know if you did the right thing if in the Groups admin, the Access Type is custom. if it is public, it confusing is not what you think. That just means public to the inside of the company. There really should be an "external" type to make it clearer.