Here is what I do for this (I am using this pattern for sending emails and assigning Flow tasks):
1) Initialize a variable of type string called "SendEmailTo"
2) Use the SharePoint HTTP call (i try to do everything using the Group ID)
3) Use the Parse Json action against the body of the SharePoint Http using the schema in the attached file
4) Do an Apply to Each on the body of the Parse Json action, and append the email (IMPORTANT with a semi colon) to your variable. This is will built you a string of email addresses that can be used in the send email action.
SCHEMA FOR PARSE JSON ACTION
{
"type": "object",
"properties": {
"d": {
"type": "object",
"properties": {
"results": {
"type": "array",
"items": {
"type": "object",
"properties": {
"__metadata": {
"type": "object",
"properties": {
"id": {
"type": "string"
},
"uri": {
"type": "string"
},
"type": {
"type": "string"
}
}
},
"Alerts": {
"type": "object",
"properties": {
"__deferred": {
"type": "object",
"properties": {
"uri": {
"type": "string"
}
}
}
}
},
"Groups": {
"type": "object",
"properties": {
"__deferred": {
"type": "object",
"properties": {
"uri": {
"type": "string"
}
}
}
}
},
"Id": {
"type": "number"
},
"IsHiddenInUI": {
"type": "boolean"
},
"LoginName": {
"type": "string"
},
"Title": {
"type": "string"
},
"PrincipalType": {
"type": "number"
},
"Email": {
"type": "string"
},
"IsEmailAuthenticationGuestUser": {
"type": "boolean"
},
"IsShareByEmailGuestUser": {
"type": "boolean"
},
"IsSiteAdmin": {
"type": "boolean"
},
"UserId": {
"type": "object",
"properties": {
"__metadata": {
"type": "object",
"properties": {
"type": {
"type": "string"
}
}
},
"NameId": {
"type": "string"
},
"NameIdIssuer": {
"type": "string"
}
}
}
},
"required": [
"__metadata",
"Alerts",
"Groups",
"Id",
"IsHiddenInUI",
"LoginName",
"Title",
"PrincipalType",
"Email",
"IsEmailAuthenticationGuestUser",
"IsShareByEmailGuestUser",
"IsSiteAdmin",
"UserId"
]
}
}
}
}
}
}
