The following single line of code produces this error:

Messaging.reserveMassEmailCapacity(1);

When I omit this and actually send a mass email, Messaging.sendEmail returns success in the SendEmailResult list (isSuccess == true). However, the email doesn't actually send and instead I get the following email:

Mass email request "Mass Email (API)" failed.
The system returned an error code of "INSUFFICIENT_EMAIL_ACCESS".

You do not have the level of access necessary to perform the operation you requested. Please contact the owner of the record or your administrator if access is necessary.

Click http://na9.salesforce.com/07AE0000000CbZW to view more details about this mass email request.

Best Regards,
Salesforce.com
www.salesforce.com



Clicking on the link takes you to a page that simply displays the following:

Insufficient Privileges You do not have the level of access necessary to perform the operation you requested. Please contact the owner of the record or your administrator if access is necessary.


I'm running as a System Administrator, from within Apex.The email is just a test and should be sent to one user, which is me in this test case. When I send as a single email it works fine. Following is the code for sending the mass email:

// Reserve email capacity for the current Apex transaction to ensure
// that we won't exceed our daily email limits when sending email after
// the current transaction is committed.
//Messaging.reserveMassEmailCapacity(userIds.size());
// TODO: Report error to Salesforce? This method results in an unauthorized error.
	
// Create a new single email message object 
// that will send out a single email to the addresses in the To, CC & BCC list.
Messaging.Massemailmessage mail = new Messaging.Massemailmessage();
	
// Specify the address used when the recipients reply to the email.
mail.setReplyTo(o.EmailReplyTo__c);
			
// Specify the name used as the display name.
mail.setSenderDisplayName(o.EmailSenderDisplayName__c);
				
// Apply template.
mail.setTemplateId(o.EmailTemplateId__c);
			
// SaveAsActivity must be false when sending email to users
mail.setSaveAsActivity(false);

// Set target object Ids
mail.setTargetObjectIds(userIds);
	
// Send the email.
Messaging.sendEmail(new Messaging.Massemailmessage[] { mail }, false);

Any help would be greatly appreciated.

Thanks in advance,

Adam Purkiss