IneoSmtp.Smtp.SendMailOffice365GraphParameters sendMailOffice365GraphParameters = new Smtp.SendMailOffice365GraphParameters
(
    "ClientId",
    "ClientSecret",
    "Tenant",
    "UserId"
);
IneoSmtp.Smtp smtp = new IneoSmtp.Smtp
{
    SendMailOffice365GraphParams = sendMailOffice365GraphParameters,
    SenderEmail = "sender@mail.com",
    Recipient = "\"Paul Petit\"<destinataire1@mail.com>",
    CC = "destinataire2@mail.com",
    Subject = "Test de mail via Office 365",
    Filenames = @"C:\Test\test.pdf",
};
if (smtp.SendMail())
    MessageBox.Show("OK");
else
    MessageBox.Show(smtp.Error);