1. Apex Scheduler 
2. Batch apex 

global class ApexScheduledClass Implements Schedulable
            {
                        global void execute(SchedulableContext sc)
                        {
                                    sendmail();
                        }
 
                        public void sendmail()
                        {// Please add your logic according to requirement
                                    Messaging.SingleEmailMessage email = new Messaging.SingleEmailMessage();
                                    string [] toaddress= New string[]{'demo@gmail.com'};
                                    email.setSubject('Testing Apex Scheduler-Subject');
                                    email.setPlainTextBody('Testing Apex Scheduler-Body');
                                    email.setToAddresses(toaddress);
                                    Messaging.sendEmail(New Messaging.SingleEmailMessage[]{email});
                        }
            }

global class InactiveApplication implements Database.Batchable<sObject>
{
    global Database.QueryLocator start(Database.BatchableContext BC)
    {
        String query = 'Select Id, Name, Owner.Email from Trade_Ally_Account__c where Stage__c = 'Prospecting' and LastModifiedDate = LAST_N_DAYS:31';
        return Database.getQueryLocator(query);
    }
 
    global void execute(Database.BatchableContext BC, List<Trade_Ally_Account__c> scope)
    {       
        EmailTemplate emailTemplate = [select Id, Body from EmailTemplate where DeveloperName = 'Update_Service_Request'];
        
        for(Trade_Ally_Account__c ta : (List<Trade_Ally_Account__c>)scope) {
            Messaging.SingleEmailMessage email = new Messaging.SingleEmailMessage();
            email.setToAddresses(new String[] {ta.Owner.Email});
            email.setSaveAsActivity(false);
            email.setTargetObjectId(ta.OwnerId);
            email.setTemplateId(emailTemplate.Id);
            email.setWhatId(ta.Id);
            Messaging.sendEmail(new Messaging.SingleEmailMessage[] {email});
        }
    }  
    global void finish(Database.BatchableContext BC)
    {
    }
}