May 19, 2024

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Kerio Connect: Issue with Email Delivery

If you’re using Kerio Connect for your email server, you may encounter issues with email delivery from time to time. Email delivery issues can be frustrating, especially if you rely on email for business communications. In this post, we’ll discuss some common reasons for email delivery issues in Kerio Connect and how to resolve them.

DNS Configuration Issues:

The translation of domain names into IP addresses is the responsibility of DNS (Domain Name System). If your DNS configuration is incorrect or outdated, your email server may not be able to deliver emails to the correct recipient. To fix this, check your DNS settings in Kerio Connect and make sure they are correct.

Firewall Blocking: 

Your firewall may be blocking outgoing emails from Kerio Connect. This is a common issue that can be resolved by checking your firewall settings and allowing outbound email traffic. Verify that the incoming email traffic has the correct IP address and port number.

Spam Filters: 

The email service provider of the recipient might mark your emails as spam. If your emails contain particular keywords, links, or attachments, this might happen. To avoid this, make sure your emails are not spammy and follow best practices for email marketing.

Blacklisted IP Addresses:

 If your IP address is blacklisted, your emails may be reject by the recipient’s email provider. To avoid this, check if your IP address is blacklist by using a free online tool. If it is, contact your ISP (Internet Service Provider) and request to have your IP address removed from the blacklist.

Email Size Limitations:

 Your emails may be rejected if they exceed the recipient’s email size limit. To avoid this, check the size limit for emails set by the recipient’s email provider and make sure your emails comply with it.

Server Overload:

 Your email server may be overload with too many emails, causing delays in email delivery. To fix this, you can increase the processing power of your server or limit the number of emails sent at one time.

Incorrect Email Address:

One of the most common reasons for email delivery issues is an incorrect email address. Verify that the email address of the recipient is correct and free of any typos or errors. Additionally, ensure that the recipient has not deactivated the email address.

SMTP Authentication: 

SMTP authentication is necessary for email delivery in Kerio Connect. If SMTP authentication is not configured properly, your emails may be reject by the recipient’s email provider. To fix this, check your SMTP verification settings and ensure they are right.

Email Routing:

 Email routing is another important aspect of email delivery in Kerio Connect. Make sure that your email routing settings are configure correctly and that the emails are route to the correct destination.


Some email providers use greylisting to combat spam. Greylisting temporarily rejects emails from unknown senders and waits for the sender to try again. This can cause delays in email delivery, but the emails will eventually be deliver if the sender tries again.

Email Content Filtering: 

Kerio Connect has a built-in content filter that blocks emails containing certain keywords or attachments. Make sure that your emails comply with the content filter rules to avoid email delivery issues.

Email Reputation: 

Your email reputation can also affect email delivery. If your email reputation is poor, your emails may be reject by the recipient’s email provider. To improve your email reputation, follow best practices for email marketing and avoid sending spam emails.

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