Overview

When setting up the Kerio account via an external mail server, the Domain forwarding needs to be configured. Kerio Connect uses login credentials defined in the SMTP relay server settings for domain forwarding.

At times, email forwarding may not be working properly, and you may encounter the following message in the Warning logs:

Sent reply to RCPT: 550 5.1.1 Mailbox <username@domain.com> does not exist

Prerequisites

Access to Kerio Connect Webadmin is required.

Diagnosis

For the email domain forwarding to be working properly, you need to use the same server as the custom SMTP relay and the forwarding SMTP relay. There is no option to enter credentials at Domain > Forwarding, but Kerio Connect will use the credentials defined at SMTP Server > SMTP Delivery if the target server is the same.

Solution

Log in to the Webadmin interface.
Navigate to Configuration > Domains.
Double-click on the necessary domain and select the Forwarding tab.
Enable If the recipient was not found in this domain, forward the message to another host option and specify the Mail server name and port.
Choose the Delivery option. The default option is Online - Deliver the messages immediately. Click OK.
Navigate to Configuration > SMTP Server > SMTP Delivery.
Click on the Add button to create a new SMTP relay rule.
Enter a Description, select the Always use this relay server option, enter the server details:
- Hostname
- Port
- User
- Password
Click OK to save the settings.
(Optional) If the server cannot be used as the default relay server, the emails might be rejected because of the enabled Antispoofing protection. The workaround is to include a 3rd-party Mail server into the Local clients IP address group.