If your mail server is temporarily unreachable, our service continues to accept incoming emails, securely stores them temporarily, and automatically attempts redelivery. Initially, this occurs about every 5 minutes, later at longer intervals. You can view the individual delivery attempts in the Email Live Tracking. If you have subscribed to the Continuity Service, you can continue to work with your emails during the outage via the Webmail.

When Will the Next Delivery Attempt Occur?

If your mail server is temporarily unreachable, our service continues to accept incoming emails, stores them temporarily, and automatically delivers them as soon as your server is reachable again.

The following rules apply to storage and delivery attempts:

• Incoming emails are temporarily stored for up to 7 days.
• Outgoing emails are temporarily stored for up to 24 hours.
• The interval between delivery attempts initially is a few minutes and then increases linearly, so that several hours may pass between individual attempts.

The further behavior depends on your mail server's response:

• In the case of a temporary error (4xx), e.g., when the server is temporarily unreachable, delivery is retried as described above. If the email cannot be successfully delivered within the respective storage period, the sender receives a non-delivery report (NDR).
• In the case of a permanent error (5xx), a non-delivery report (NDR) is immediately generated and sent to the sender. No further delivery attempts are made.

Where Can I See the Individual Delivery Attempts?

You can view the individual delivery attempts in the Email Live Tracking module:

1. Open the Email Live Tracking module.
2. Open the details of the affected email.
3. Click on the SMTP tab.

There you will see the individual delivery attempts with timestamps and SMTP status codes:

What Can I Do During the Outage?

To bridge the incoming storage period of 7 days and remain operational during an outage, we recommend using the Continuity Service.

If you have subscribed to the Continuity Service, your emails will be immediately redirected to our service Hornet.email upon the first complete unreachability of your mail server.

During the redirection, your mail server’s availability is continuously monitored. As soon as your server is reachable again, the redirection ends and all emails caught by the Continuity Service during the outage are delivered to your mail server.

Additionally, the Continuity Service automatically archives all email traffic for 3 months.

You can access the web portal at: webmailer.hornetsecurity.com

Note: Emails caught by the Continuity Service during the outage will permanently retain the status deferred in Email Live Tracking, even after successful delivery to your mail server. This is normal, system-related behavior and not an indication of a delivery problem.