I have the issue SINGLE_EMAIL_LIMIT_EXCEEDED and after running this code from anonymous but have the same issue.
I am using setTargetObjectId then it not be count in the limit and mail send successfully.
But not working ??

Messaging.SingleEmailMessage emailMsg = new Messaging.SingleEmailMessage(); emailMsg.setTargetObjectId(contactid);
emailMSg.saveAsActivity = false; emailMsg.setSenderDisplayName('sender name'); emailMsg.setSubject('some subject'); emailMsg.setBccSender(false); emailMsg.setUseSignature(false); emailmsg.setPlainTextBody('email body'); Messaging.sendEmail(new Messaging.SingleEmailMessage[] { emailMsg })