Our servers will queue your email for up to 120 hours (5 days). The senders will get their first bounce message after the message has been in the queue for 4 hours, saying that the message has not yet been delivered but that we will keep trying.

If your mail server is going to be down for longer than 5 days, please contact us so that we can backup your queued mail so that it is not lost.

The default behavior is for the servers to try redelivering each message every 30 minutes. As a result, half an hour after your mail server is back up, you should have recevied all of your queued email.

There are two unique circumstances where your email will not be queued, because you have directed our mail server not to queue it:

1. SMTP 5.x ERROR: Queing will result if your mail server is completey unavailable, or replying with a temporary SMTP (4.x) error. However, if your mail server is responding fine and someone has directed your mail server to reject a message at the SMTP level and tell our mail server to not try delivering the message again (5.x error), then this is seen as a permanent error. Our mail server will do what it's told and not try again, deleting the message from the queue. A Delivery Status Notification (DSN) will be "returned" to the sender. As a result, if you find that you have to "reinstall" your mail server, please ensure that it is fully configured and tested to accept email before putting it back online at the same IP address to prevent losing email once the mailserver goes back online.

2. NXDOMAIN: Queing will result if you have specified a hostname as your Customer Mail Server under Mail Server Settings, and the hostname is temporarily not resolving. This happens when the authoritative nameservers for the domain are either completely unavailable, or replying with a temporary error. However, if the authoritative nameservers are responding fine, and someone has directed them to say that the hostname doesn't exist (NXDOMAIN), then this is seen as a permanent error. You have told the public that this hostname doesn't exist. As a result, our mail server will not continue trying to send anything there, resulting in any messages to this host being removed from the queue. A Delivery Status Notification will be "returned" to the sender.