Dear sir I assume these conditions are true.
1.sample domain: test.com 2.test.com has one mx is called mail.test.com 3.mail.test.com host is down if some one relay an email which sender is some...@test.com ,recipients is some...@test.com via one mailrelay server.After mailserver recieve a message it try to connect to test.com 's mx ,finally it will fail so mailserver keep a message for next retry but it will faill every times until a message is expire.After that mailserver will generate delivery status notification,send it back to sender some...@test.com with hope to notify sender that his/her message can not be delivered but It can not connect to test.com 's mx and retry until message is expire.Default value for postfix queue expire time is 5 days if someone send only 1 message which all situation are met these conditions.It will stay in mailserver for 10 days.what 's happen if someone send 10,000 messages/day.Are there any solution ? Jittinan Suwanrueangsri
