Articles

IMAP, POP3 configurations, SMTP server-client communication

• Unable to Send Emails with Outlook to Users on External Domains

  Overview When an user with a Kerio Connect mailbox sends an email to an external email address using Microsoft Outlook, the message is being rejected by Kerio Connect because the user cannot relay thr...

• "No reverse DNS" problems while sending over port 465

  Overview Some of the users can't send emails via secure SMTP port 465. Kerio Connect blocks the authentication and the Security log shows the following error: Client with IP address X.X.X.X has no rev...

• Email from IP address was rejected because of missing authentication

  Overview When trying to setup an email service from an external source/provider (eg: Gmail, Sendmail, Mailchimp, Postfix, etc.) in Kerio Connect and the provider is set up to dual delivery mode, Kerio...

• Secure IMAP service is not listening in Windows

  Overview When starting Secure IMAP service in Kerio Connect, the port might be already occupied by another service or process. Other preinstalled Windows programs may cause start problem for IMAPS por...

• 5.4.4 Host not found

  Overview While trying to send emails to a specific address, Kerio Connect generates the following Mail Delivery Subsystem notification: Result: failed, Status: 5.4.4 Host not found, Remote-Host: 127.0...

• Email Rejected 550 Please Use a non-generic PTR

  Overview While attempting to send emails to the external, not Kerio Connect domains, the message is being returned with the following entries in the Mail logs: Result: failed, Status: 5.4.0 550-PTR (r...

• Debugging Internal Email sending and routing

  Overview While trying to configure Kerio Connect accounts to work concurrently with external providers such as O365, Gmail, etc, the message sending and receiving is not working for both providers tog...

• MXtoolbox Domain Health problems

  Overview While performing the MXtoobox domain check, the tool returns the response about problems with SMTP Banner, Reverse DNS mismatch, SMTP TLS, and transaction time. These settings can be checked ...

• Troubleshooting SMTP-Related Issues

  Overview   Occasionally, you may encounter issues where email delivery is unsuccessful due to SMTP errors. This article provides information about the root causes and resolution for known SMTP queries...

• Email Domain Forwarding

  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...