FuelPHPのTaskとEmail

FuelPHPにて
タスク内でEmailパッケージ（SMTPドライバ）を使いメール送信をしたいのですが、上手くいきません。

タスク以外では正常に送信できます。
（restコントローラーにて、同様の設定でEmailパッケージを使用）
サーバーはAmazon EC2、メールサーバーとしてAmazon SESを使用しています。

エラーログは以下です。

Uncaught exception Email\SmtpCommandFailureException: Got an unexpected response from host on command: [QUIT] expecting: 221 received
Callstack:
#0 fuel/packages/email/classes/email/driver/smtp.php(190): Email\Email_Driver_Smtp->smtp_send('QUIT', 221)
#1 fuel/packages/email/classes/email/driver/smtp.php(35): Email\Email_Driver_Smtp->smtp_disconnect()
#2 fuel/core/base.php(458): Email\Email_Driver_Smtp->__destruct()
#3 fuel/core/base.php(458): Fuel\Tasks\Sendmail->send_immediately('1')
#4 fuel/packages/oil/classes/refine.php(108): call_fuel_func_array(Array, Array)
#5 [internal function]: Oil\Refine::run('sendmail:send_i...', Array)
#6 fuel/packages/oil/classes/command.php(126): call_user_func('Oil\Refine::run', 'sendmail:send_i...', Array)
#7 oil(68): Oil\Command::init(Array)
#8 {main}

Previous exception:
Uncaught exception Email\SmtpCommandFailureException: Got an unexpected response from host on command: [HELO localhost.local] expecting: 250 received:
#0 fuel/packages/email/classes/email/driver/smtp.php(144): Email\Email_Driver_Smtp->smtp_send('HELO localhost....', 250)
#1 fuel/packages/email/classes/email/driver/smtp.php(64): Email\Email_Driver_Smtp->smtp_connect()
#2 fuel/packages/email/classes/email/driver.php(894): Email\Email_Driver_Smtp->_send()
#3 fuel/app/tasks/sendmail.php(35): Email\Email_Driver->send()
#4 fuel/core/base.php(458): Fuel\Tasks\Sendmail->send_immediately('1')
#5 fuel/packages/oil/classes/refine.php(108): call_fuel_func_array(Array, Array)
#6 [internal function]: Oil\Refine::run('sendmail:send_i...', Array)
#7 fuel/packages/oil/classes/command.php(126): call_user_func('Oil\Refine::run', 'sendmail:send_i...', Array)
#8 oil(68): Oil\Command::init(Array)
#9 {main}