使用 PHPMailer 解決輸出 MIME 格式的問題 https://www.mxp.tw/8635/

google_gmail_api_with_phpmailer.php

<?php
$service = new Google_Service_Gmail($client);
try {
	$mail = new PHPMailer();
	$mail->CharSet = "UTF-8";
	$mail->From = "發信端信箱";
	$mail->FromName = "發信端別名";
	$mail->AddAddress("收信端信箱", "收信端別名");
	$mail->AddReplyTo("回信端信箱", "回信端別名");
	$mail->Subject = "信件主題";
	$mail->Body = "信件內文";
	$mail->isHTML(true);
	$mail->preSend();
	$mime = $mail->getSentMIMEMessage();
	$mime = rtrim(strtr(base64_encode($mime), '+/', '-_'), '=');
	$mensaje = new Google_Service_Gmail_Message();
	$mensaje->setRaw($mime);
	$service->users_messages->send('me', $mensaje);
} catch (Exception $e) {
	print($e->getMessage());
}