curl --location --request GET 'https://gmail.googleapis.com//gmail/v1/users//settings/sendAs//smimeInfo'
{
"smimeInfo": [
{
"encryptedKeyPassword": "string",
"expiration": "string",
"id": "string",
"isDefault": true,
"issuerCn": "string",
"pem": "string",
"pkcs12": "string"
}
]
}