public static void sendMail(List<Campaign> Campaigns){
    for(Campaign camp:campaigns){
        //New instance of a single email message
        Messaging.SingleEmailMessage mail = new Messaging.SingleEmailMessage();
        // Recipient
        mail.setTargetObjectId(camp.CreatedById);
        // Set the mail template
        mail.setTemplateId('00X26000000DbPe');
        mail.setBccSender(false);
        mail.setUseSignature(false);
        mail.setSaveAsActivity(false);
        //mail.setWhatid(camp.Id);
        Messaging.sendEmail(new Messaging.SingleEmailMessage[] { mail });
    }
}