There are multiple reasons why no incoming emails arrive in Kerio Connect. This article serves as a guide on what to check when such an issue occurs.
Access to Kerio Connect Administration User Interface (UI)
During the initial configuration of Kerio Connect, you are asked to input the hostname of the Kerio Connect server. The hostname should be valid, which means an A record that points to the Public IP of the Kerio Connect server must exist in the DNS.
Here is an example of A record:
In Kerio Connect, you can verify the hostname in Dashboard or in Configuration > Domains.
To change the hostname, go to Configuration > Domains and click the Internet Hostname button.
The MX record (Mail Exchanger record) tells mail servers where to route emails. This is typically pointed to the hostname of Kerio Connect. If a relay or email gateway is used, the MX record will be pointed to the relay or gateway’s hostname. You can use MXToolbox to check the MX Records for your domain.
Note: Changes in DNS records may take up to 48 hours to propagate.
SMTP Port (25)
Public Mail servers communicate via the SMTP Port 25, so this port should be open.
In Kerio Connect Administration, go to Configuration > Services and make sure that the SMTP Service is running. Make sure that no other application using Port 25 is running on the server.
If there is a firewall in front of Kerio Connect, the firewall must be configured to forward incoming Port 25 traffic to the local IP of Kerio Connect. The Built-in Firewall in the OS must also be checked.
The best way to check if a port is open is via telnet:
Port is open:
Port is closed: