Articles

IMAP, POP3 configurations, SMTP server-client communication

• 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...

• 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...

• 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...

• Email from Google IP address was rejected because of missing authentication

  Overview When an external provider Gmail is set up to dual delivery mode, Kerio Connect may experience SMTP authentication problems. The Gmail IPs should be added into SMTP relay and Anti-spoofing whi...

• "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...

• Mail server relay retry interval for SMTP authentication

  Overview The user with a mailbox on the Kerio Connect server sends an email to external email address. The message is being rejected by the Kerio server because the user cannot relay through this serv...