Salesforce apex发email的小细节

用apex发email的做法，在developer guide上有具体例子，比如：

Messaging.SingleEmailMessage message = new Messaging.SingleEmailMessage();

// Set recipients to two contact IDs.

// Replace IDs with valid record IDs in your org.

message.toAddresses = new String[] { '003D000000QDexS', '003D000000QDfW5' };

message.optOutPolicy = 'FILTER';

message.subject = 'Opt Out Test Message';

message.plainTextBody = 'This is the message body.';

Messaging.SingleEmailMessage[] messages =

new List<Messaging.SingleEmailMessage> {message};

Messaging.SendEmailResult[] results = Messaging.sendEmail(messages);

if (results[0].success) {

    System.debug('The email was sent successfully.');

} else {

    System.debug('The email failed to send: '

+ results[0].errors[0].message);

}

照猫画虎，结果出问题了：

System.EmailException: SendEmail failed. First exception on row 0; first error: NO_MASS_MAIL_PERMISSION, Single email is not enabled for your organization or profile.:

搜了一下原因如下：

"Email Administration - Deliverability - Access level" 这个地方需设置成 "All email"